I love this idea, and I hope that it develops further. I also agree that there should be a comments section for each individual build, rather than a messy mass of comments for all of them. This would make it easier for people researching a particular PC build by allowing them to see only relevant comments.
I built a home theater PC for a friend a year ago, and she and I have both been very happy with the results. Looking at your build for a HTPC, I would like to offer a few suggestions/differing opinions.
I selected an Athlon 64 X2 5050e for her processor, and it has been amply powerful to handle Blu-ray playback (with GPU assistance, of course) as well as all other theater needs thus far. It is an energy efficient model, suggesting that it should run cooler (and thus create less noise from cooling) and should be easier on the electric bill than the Pentium G6950 processor that you selected. It is also cheaper than the Pentium, selling on Newegg for $62.99 when I purchased it a year ago, and going for $67.99 currently on ZipZoomFly (it is, unfortunately, no longer listed on Newegg). Better prices for this processor might be available given further searching. Additionally, if you wanted to cut costs further, I am confident that you could step down to a 4850e (and likely lower) with no negative impact to Blu-ray and HD playback.
The Radeon HD 5750 does seem to be a little overkill for an HTPC unless you intend the system to be capable of some casual gaming. However, I can understand this choice if it was for it's ability to bitstream Dolby TrueHD and DTS-HD Master audio. I have not researched this matter in the last year, so I am not aware of what offerings are currently out there.
For my friend's HTPC, I selected instead the S3 Chrome 530 GT, which was reported to be able to pass full-quality audio from Blu-ray discs over HDMI with a price tag of only $50. I have had mixed results with this card, however, and I would not recommend it after having used it myself.
Fortunately, I had a backup option in place in case the Chrome 530 GT didn't pan out. The motherboard (an ASUS M3N78-EM Micro ATX) sports an on-board Geforce 8300 and HDMI port, which I selected because there are numerous guides across the internet detailing how to decompress a hi-def, copy-protected audio stream (such as Dolby TrueHD and DTS-HD Master on Blu-ray discs) on the board before sending it over an optical connection to the receiver, allowing full-quality audio playback. For those that are comfortable around their technology (as most Tom's readers likely are), this is a cost-effective solution that has worked very well for my friend's setup. For those not quite as comfortable with technology who are still setting up an HTPC themselves, the Radeon HD 5750 may be the right pick after all, provided that there isn't a cheaper card available capable of doing the same job (again, something I haven't personally researched in some time).
The SSD in your build isn't a bad idea, but it might be more expensive than necessary for most people. I opted for a HITACHI Travelstar 5K250 160GB 5400 RPM laptop hard drive, selected using Tom's hard drive charts for its energy efficiency. Between the drive and the 2.5" to 3.5" adapter to mount it in the case, it totaled a little under $68. While an SSD probably would result in a generally snappier system, I find that the limiting factor in responsiveness on my friend's HTPC is DVD/Blu-ray spin-up times or network latency (when streaming off the media server). For all intents and purposes (i.e. when I don't have my ear pressed up against the computer case), this drive has been silent and in all other ways sufficient for the system's needs. For anyone with money to burn, I would still concede that the SSD is a good choice, but for the average consumer, I would still recommend a carefully-selected magnetic drive.
I would also recommend including a TV tuner card in your list of HTPC components. This is an optional component, but it is something that I think everybody should give good consideration if they are building a HTPC. These cards won't be able to pick up every station on a satellite or cable service, so it is probably not a worthwhile purchase for anyone that plans to continue with such a subscription. But if your plan is to ween yourself off of subscription television in favor of online streaming services, then a TV tuner can help fill some of the gap by giving you the option to record over-the-air programs. For my friend, I spent about $140 for a dual-tuner card.
Input peripherals may be outside the scope of these articles, but they are an important consideration for home theater setups. For a desktop computer, it's entirely up to personal taste when choosing a mouse and keyboard. For a HTPC, however, you have to consider that you will usually be sitting across the room from your PC, and most wireless keyboards/mice can have difficulty over such distances (even at 10 feet, many products I've tried have struggled). Additionally, full-sized peripherals can be unwieldy on the couch. One option is to go with a small, all-in-one input device, such as the Logitech diNovo. Another, less-expensive approach, would be to use a short-range mouse/keyboard, whether it's wired or just cheap wireless, while using a PC remote control when sitting on the couch.
As somebody suggested earlier, it might be prudent to include pricing for the operating system used. While in most PCs this can be an assumed cost that varies according to the user's preference in operating systems (after all, Linux is free, right?), it bears special mention in HTPCs. If the system is not intended to handle Blu-ray playback at full quality, then any operating system will do. But Windows, to the best of my knowledge, is the only OS available right now that will allow HDCP passthrough, meaning that it is also the only OS capable of playing Blu-ray discs at full resolution and full audio quality without inconvenient and sometimes unreliable workarounds (such workarounds involve ripping the disc to the hard drive to remove any copy protection).
I apologize for the long post, but you did ask for suggestions and ideas. Hopefully, this information could help you cut the cost of your build down even futher without sacrificing any performance. Again, I haven't researched this topic heavily in almost a year, so there may be even better solutions today than any of my recommendations, but I think a lot of the information is still relevant. To reiterate, my friend and I have been very happy with her home theater PC. It plays back Blu-ray, DVDs, online Flash, over-the-air TV, and other videos all very smoothly. And with a couple of wireless gaming controllers, it has also been great fun for emulating old games on the big screen for nostalgic get-togethers.