[citation][nom]Gulli[/nom]Packard Bell is one of those vendors, they're pretty big, the HD 6670 is not a $100 GPU and the PSU of a $300 pre-built may say it supplies 250W, but unless almost all of that goes on the 12V rail the PSU will fry with a HD 6670, even if the PSU lives up to its specifications, which they often don't and you have no way of knowing beforehand because there are no reviews of these obscure OEM-PSUs available and tough luck getting even the name and brand of an OEM-PSU (they don't let you open the case in the store and the clerk probably doesn't know either). Then we're still left with weird motherboard incompatibilities and cases that cannot provide sufficient cooling or don't even fit the GPU physically.[/citation]
Packard Bell doesn't exist, at least not in the U.S. anymore. But this is like any project, a consumer who does their research will avoid problems.
My point is simply that if you are talking about true, ultra budget computers, the home builder can't beat their price without engaging in some funny accounting (committing a legal OS license, mouse and keyboard, card reader, etc). Both Dell and HP can sell you a complete, working out of the box system for approximately 300 dollars. Dell will even offer it in a desktop case that will accommodate a reasonably sized graphics card upgrade (HP pushes their slimline cases which are a bit of a dead end).
This is a hard price point for a home builder to hit without cutting a lot of corners themselves (sketchy PSU that comes with a low end case bundle, etc.). There are numerous graphics cards out now for under a 100 dollars that are single slot and require no additional power connecters that have performance around that of a 4850--plenty for gaming at 1650 or (more likely given the tight build budget) 1368. Many of these can be powered by the PSUs that come with an OEM system.
Basically, your looking at 375-400 dollars total build for a system that will let you use medium settings in most games (or better at 1368).
Can a home builder to better?
Yes, with a lot of creative tricks (upgrade license), bundle selection, recycling of keyboard and mouse, but it's not that dramatically better.
As I've stated before, I think the interesting question is at what budget do things really start to swing in favor of the home builder over OEM. My guess is that it's around 550-600 dollars but that's just a guess.
And neither Dell nor HP void a warranty because you open their desktop cases. In fact, if there are problems with their builds, they'll often send you the replacement parts and have you open and do the repair yourself.
And just for the record, I'm an avid home builder who has built almost all of his own PCs and (and those for friends and family). I am also thoroughly annoyed by a locked BIOS and a 250 wtf power supply but that doesn't mean I can automatically write off all OEM computers and not see that there are certain budget ranges where they have a place.