What kind of memory is appropriate for Phenom II

My situation:

I just purchased a AMD Phenom II X4 810 @2.6GHz (OC'd: 3.09GHz) and am currently running with 8gb of DDR2 RAM @ 667Mhz on a Gigabyte MA790X-UD4P Motherboard. My motherboard apparently does not support DDR3 despite the fact that it says 'AM3' on the box, Odd I know.

My question(s):

Would it be worth it to upgrade my memory speed to 1000Mhz, seeing as to how my processor is relatively high end ( I think )? Would it scale well with my build as stated above? What should I be shooting for as far as RAM is concerned?

note: the manufacturer of my motherboard boasts a maximum of 16Gb DDR2 at 1333Mhz+

I disagree somewhat. I think you would see a significant difference moving from ddr2 667 to ddr2 1066 speeds. I noticed a difference moving from 800 Mhz to 1066Mhz in my testing. I tested using several benchmarks, including sandra, AOD, pcpitstop, pcmark, and 3dmark06. Unfortunately that was some time ago, and I don't have numbers to share. But I believe it was in the 5-10% range increased performance.

And I'm not sure what performance gains there are moving from 4GB of ram to 8GB. You would have to have an application that would use more than 4 gigs of ram. There's just not that many apps that do that.

Is it worth it? That's up to you, 4 gigs of ram is running ~80-100 US. I recommend OCZ, reapers in particular if you can fit them with your cooling setup. 5-5-5-15 for 1066 Mhz ram.

Yeah Ive heard that OCZ is great for overclocking as well. My computer is mostly a gaming/photoshop machine, taking that into consideration; if you were in my position, would you invest in a video card upgrade over new RAM? ( My current video card is a PNY GeForce 9800GT 512mhz )