As far as gaming goes the answer is no they are not quality gaming computers. I owned one, and I can tell you the machine needed a major overhaul in under six months. I found issues in the graphics card, the system ram, the plug and play, and slot allotment. There are a lot of places to cut corners in a personal computer, and Sony did a great job in finding all of them.
They had a generic graphics card with outdated support. Specifications can be deceptive. Without quality driver support you will find yourself in a bind, and no I am not just talking about updated drivers, but the entire catalog of drivers being available.
The memory was equally laughable. You would think that with two slots they might only fill one, but they filled both. Meaning when it came time to upgrade the memory I was not doubling it. I was only increasing it by twenty five percent. That may seem minor, but it definitely made the whole process more expensive, and as we all know memory isn't cheap.
Mind you I was not purchasing a low end computer either. I shelled out a good eighteen hundred dollars. So to fork out another two hundred dollars more in parts just to play a new game that wasn't even particularly intensive was a real kick to the crotch.
Beyond this I have no real complaints with the system. The machine as a whole was quite reliable, and the software included was quite decent. In fact it held up exceedingly well for the use I put it through. I just did not like the fact that it was not upgrade friendly, and Sony cut corners.
I would say however if your serious about gaming its just going to be better to pay up front for what your going to need. Make sure your getting a name brand model card, and know about the systems ram, and the available slots, and how they are being used. Your not going to save money if your going to be replacing a card immediately, and replacing all the RAM.
Erm...I don't know where you're shopping but I bought 4gb ddr2 800mHz RAM (not fast but hey, its 4gb for cheap) for $30 from Frys with a $20 mail-in rebate! RAM is not cheap, in this case it was $10 for 4GB. They're readily available as 2x2GB sticks for about $40, which is chump change when talking about PC components.