I've got a $70 dollar gift/debit card burning a hole in my wallet.

Which part of my pc would be in largest need of an upgrade?

CPU: Intel Q8300
GPU: 250 GTS 1gb
Ram: 8 gigs ddr2 (no brand-Asus?)
PSU: 1000 watt, just upgraded
HD: 750 gb, 50 gb left
Mobo: ASUS CG5270
Case: ASUS CG5270

There doesn't seem to be much info on the mobo other than being linked to the pc it came with, the CG5270-BP003, but I sure hope it has a more standard name, since I'd need to know it to find the right BIOS update.

The case is pretty bothersome too. The sides are perforated and really thin, so the fans (that I had to buy separately -.-) are really loud. Its size is huge, and the inside is pretty barebones. Also, poor ventilation.

I was disappointed that the mobo didn't support SLI though, although atm, my single card is doing just great.

I'm thinking either the mobo or the case. However, with a new motherboard, I'd either be stuck with socket 775 or have to upgrade to 1366/1156 (ddr3 can wait, lol). And while the q8300 is the shittiest of the shittiest of quadcores, or so it seems, it's good enough for almost all my games maxed.

I've never had any experience upgrading cases though. Is it generally a good idea?

How about top vs bottom psu's in cases?
How high up in price should I go? 60? 100? More?

Anything would help. I'd just like to learn more.