I would not recommend PhysX. The power draw isn't worth the performance return IMO. If I were to get a PhysX card, I would get a 240 or even maybe a 220 so the power draw isn't so extreme. I know you already have the 260, so it's up to you.
You don't need 8GB ram if all you're doing is gaming.
EDIT: I would never get the 465. The 460 actually does better in certain titles. I always recommend against the 465s and 5830s. They consume almost the same power as a 470 for the same performance as the 460, for $30-$40 more than a 460, or $20-$30 less than a 470. If you want to play above 720p, I'd recommend a 470. If you're gaming at or below, get a 460 1GB.