He doesn't mention anything about latency issues so his connection isn't the problem. As for the ram, even though you are running only DDR2, it's clocked at the highest speed. It wouldn't hurt to increase your ram. Your main issue I would guess is your video card. There are a lot better cards out there that are cheap in price, I would take a look. There are known issues with FPS lag right now so I would hope they have a fix in the near future.

If you are getting the same XP for both then you are clearly not playing the objective correctly. I get 12k XP for a win and about 8-9k for a loss. That is if I join from the beginning. Joined a couple games late and only got 3k