This was an AWESOME article! Thanks to the guys at Tom's for writing it!
It looks to me like many of the people commenting either can't read, or the article went right over their heads (Woosh).
I have EXACTLY this situation at home. I have just upgraded my main computer. It might not be much of an upgrade to some of the people here, but my frame rates in Guild Wars with all the graphics turned up and running at 1680 x 1050 often hit 125, and average over 60.
So, my old system guts were used to upgrade the "guest" computer in my livingroom. This computer is for people who visit and gets used a few times a week. Currently is has a 1.5GHz Athlon 64 (not duel core) with 2G RAM and an ATI 9600XT graphics card overclocked with extra cooling on it. It will run Guild Wars at 1280 x 1024 with framerates reaching about 50 max, and hovering around 40 most of the time.
This would be the ideal system to test your performance boost on. For about $160 I could install the video card and a CPU running at around 2-2.5GHz overclocked. I don't really need the duel core for this system as it is not running the latest and greatest FPS games (I don't like FPS anyway, too many little kiddies playing). I'm sure this would give me added performance on the games I will be playing. And two of the major newer games will be Diablo 3 and Star Craft 2 which I'm sure would perform adequately with this system.
For some reason some of the commenters (apache_lives) seem to think this would be a waste of money. Since spending $150-$200 to get a few more years out of this system is a much better option than spending another $800 to $1000 (which is what I spent to upgrade my own computer), why would anyone spend that much money to upgrade a spare computer? No, I don't need more RAM, nor a better PSU. And why would my motherboard suddenly die for no reason? It's just as reliable as any other board. Obviously, some of the commenters did not read the entire article nor read the several times the author wrote in the article that this upgrade was for older AGP systems that could be used for your buddy if you have a LAN party. (aka SPARE COMPUTER). Just to mention, I don't get new rigs but continue to upgrade my computer over and over and over. I still have the awesome case I bought almost 10 years ago. Still fits everything. It has a new PSU, but otherwise it's the same case. No point replacing it for no good reason. I only replace the accessories as they wear out. The only thing I replaced that I didn't have to was my monitor. I replaced my 19" CRT with a 22" widescreen (anyone wanna buy a 19" CRT monitor cheap?)
Having said that, I wouldn't mind if Tom's could mention Wow and Guild Wars in their articles. I realize that much of the speed in a MMORPG depends on your Internet connection and the game servers, but you can plainly see the improvement in frame rates I got with my upgrade. A lot of people play the MMORPGs and would be interested to see how these components and upgrade would perform. It seems all the attention is given to FPS games.
With GW2 coming out in April 2010, I hope Tom's will pay a little more attention to MMORPGs.