Looking at the Intel motherboards they don't appear to be back compatible with my old hardrive (ATA/IDE as opposed to SATA), which would end pushing my costs up over $100 more. I was going to go with their 600 W power supply, but I had noticed no brands or specs were given for any of them... How difficult is a power supply to install yourself separately? Also are there any companies similar to Portatech with better reputations you could point me to, to compare with?
Thanks guys
After looking over the site a bit more, I realized that they charge $20 for case+PSU. You get what you pay for

You should avoid those no-name 400W and 650W PSUs at all cost, those have a nasty tendency to literally blow up your PC when delivering anything remotely approaching their nominal rating.
That 600 W PSU looks better, will deliver probably way more real load than the "650 W". But given the choice, I would prefer a brand name 350-450W PSU for the same price.
Installing a PSU is not more complicated than installing a harddrive, just follow the manual. And unless you happen to have a Dell, they will all fit
A Phenom II X4 965 + HD 5770 system will consume around 250 W under load, and that is already A LOT for a not-overclocked system with a single GPU.
You probably will run into trouble with that one if you neglect to properly ventilate your system, and if you use the stock fan it might get rather noisy. You would want to install additional fans at the rear of the case, which is a good idea anyway. Problem is, there is no information about fan mounts for the cheap cases.
This is starting to look as if all you would get out of buying a semi-assembled system from portatech is that they attach the mainboard to the case and plug in the CPU for you.
You might want to concider to assemble the system yourself, which would have the advantage that you probaly will get better quality for less money
Unfortunately I can't help you with alternative suggestions to portatech, being from Old Europe
I thought that you couldn't just pop a hard drive into a computer with a different motherboard. youd have to reinstall the system.
Good point, but in most cases the "Repair Installation" function of Windows will take care of that, which will not touch your data.