1 - yes
2 - size yes, psu I'm not sure about that. I'd get a brand name.
3 - Depends, if you want to overclock, yes. Another thing is AM2+ mobos are coming out this or next month. If you get a P35 budget board like mine, it will last a generation or two. It supports 45nm & fsb 1333 cpus.
Hiper is a Tier-4 PSU, but the others akhilles listed are better. With your budget (about $900 USD?), a decent Intel system should be within reach, so I also agree with him about the P35 board. That will allow you to cheap-out on the CPU now, but upgrade later. Put your money where it matters most, in the GPU and PSU to power it all. Depending on future upgrade plans and on overclocking (which can use significantly more power), I would suggest that you should get 500W or more. Choose a PSU from tier-3 or better on this list: http://www.tomswiki.com/page/Tiered+PSU+Listings?t=anon