Items that are good now will get dirt cheap over a period of months, but the very best of the best will get more expensive in terms of gold as more people are able to afford them.
In terms of real money, I expect a surge in prices with the RMAH opening, then a lull in prices while supply catches up. I expect the economy to tank whenever someone figures out how to dupe items or effectively bot farm.
I didn't benchmark, I notice the transitions at 30fps and 60fps in terms of time per frame, i did notice it dropping below 60, but never below 30. Anything over 30 minimum framerate is playable. Anyway, I ended up capping it just above 30 to leave more resources available for streaming.
The PSU label says it can, but I wouldn't try it without tracking down a professional review(full capacity load testing w/ oscilloscope).
If you can find the UL number you can figure out who made it(pretty sure xtreme gear is just a relabel of a different brand PSU), and maybe find a review on whatever PSU it was a relabel of. The UL number should start w/ an E.
I'd be surprised if it could deliver 300w within ATX spec.
If you're upgrading GPU in an OEM you need to take a close look at replacing the PSU too, it probably can't handle high end video cards.
If you don't want to replace the PSU, try a radeon 7750, which should perform acceptably at 1080p in d3 with minimal increase in power consumption, though it probably won't perform as well in other games.