Upgrading HD and Memory

Alright, I've had my computer for a few years. All I've done to it is upgrade to 64-bit windows 7 and add a secondary hard drive. I feel like it is time to upgrade the RAM and primary hard disk.

Memory
According to the specs for my computer, the max RAM it can support is 4GB. It came with 2x 1GB sticks and 2x512MB. If i was taking it to the max, that would mean replacing the 512 with additional 1GB. That being said, memorystock's website says that my computer can handle a max of 8GB. I'm not sure if I want to spend that money now, but it would make me consider buying 2GB sticks. By the way, my motherboard (thanks Everest!) is an Intel D975XBG (Gateway OEM).

Hard Drive
I currently have a 500GB Seagate Barracuda (7200 RPM) as my primary, and the 1TB version as my secondary hard drive. I'm considering keeping the secondary drive, and replacing the 500GB one with a smaller 80 or 160GB SSD. Any advice on choosing one would be great.


Final questions: My secondary seagate hd has a 32MB cache and 3 gb/s SATA interface. Would it benefit me much to upgrade it to something like the WD Caviar Green or Black? I honestly don't know that much about how much the transfer rates or cache sizes would affect me in gaming and such.

Thanks guys...I wouldn't consider myself completely computer illiterate, but I clearly need some help.

 

So despite the fact that the manufacturer claims the maximum memory is 4GB, it shouldn't be a problem upping it to 6? Just want to make sure I don't mess up my computer when doing all of this.

 

I hate gateway...
If the motherboard and chipset both support 8GB's, what could Gateway have done to limit it to 4? I understand that if I dropped the $120ish on 2 x 2GB and it didn't work I'd be SOL, but is there a chance that it would work? Being able to pull 6GB of RAM out of this computer would be great.