I'd stay away from next-gen CPUs just now, the money you save can buy you a kick-ass video card that'll actually make a difference.
It's been a long time that I've bought a full system, and never have i spent more than a third of that budget. My current system has been built up since then, and my secondary machine only cost me about $200 CAN in supplies (mini-itx), so i'd probably get a fancy LCD screen.
btw, the ACHME PSUs in Shuttle boxes come in 150w and 200w flavors, but everything packs real tight in there. You can't go any higher, nor would you need to with the draw of any hardware you'd put in. The optical drive uses a fair amount, and a video card with a molex adapter (but i doubt most would fit).