Apire 6930 upgrade questions

Hey all. I've gotten some really good info around here, so thanks everyone that's taken the time to experiment and report and help in so many ways.

I am pondering some upgrades to my 6930 and have some questions that I haven't been able to find a definitive answer to yet.

I've upgraded my cpu from a t5800 to a t9600 and it went just fine thanks to what I learned here.

I'm hoping to upgrade the video card. From what I've gathered, the best I could hope for would be an HD4670 DDR3 card, but I'm likely to never see one. My question is, would it be a significant difference to upgrade to a 9600M GT 512MB ddr3, or am I better off waiting and watching for an HD4650 or 4670? And what significance is the ddr3 when comparing? All the benchmarks I've seen don't really indicate if it's a ddr3 9600 that's being compared to what I assume is a ddr2 4650/70.

I'm also wondering about RAM. From spec sheets, it looks like I'd be able to use up to 8gb of ddr3 RAM based on the chipset, but what is the MB restriction? I've read that 8gb of DDR2 800mhz is possible (though maybe not worth it). I'm thinking going to 800mhz probably wouldn't be worth it, unless I'm going from 2x2gb sticks to 2x4gb sticks.

Lastly, I've got another HDD on the way, which I plan to add to the second drive bay, and upgrade the main HDD to SSD. I'm assuming that would work, but I expect to be able to use max SATA II from what I've read. Is that correct?

Anyway, any help would be much appreciated. Thanks!