Comment on my gaming/work PC upgrade plan please!

I plan to do a major upgrade to my PC, replacing the mobo, CPU, GPU, and RAM. Other things like hard drives, case, CD etc will stay. I'll only replace my PSU if the 460W it provides would no longer be enough. I already have monitor/kb/mouse/speakers too.

My primary objective is gaming (and I consider myself a power gamer that likes good graphics and high FPS), but I also often concurrently run a lot of software like IDEs, some of which is CPU/RAM heavy, hence my wish for a lot of RAM and multi-core processor. For gaming purposes, my OS will probably be Vista.

Here are the components I came up with:

Motherboard:
ASUS P5Q P45/ICH10R ATX, $148.80
(details here: http://www.a-power.com/product-6275)

CPU:
Intel Core 2 Quad Q6600 2.4Ghz, $229.99

RAM:
OCZ Reaper HPC Edition OCZ2RPR10664GK 2X2G DDR2 1066MHz Dual Channel Kit, $135.99

GPU:
EVGA GeForce GTX 280, $691.50,
or
EVGA GEFORCE 9800 GX2, $566 (but then I almost definitely will have to buy a new PSU, which will pretty much offset the difference in price)

Total cost for the above 4 components: $1203

The prices are a tad on the high side, but I'm Canadian, and everything is more expensive this side of the border. I'll also have to shell out 13% tax on top of whatever number I end up with (so the real out-of-pocket expensive is about $1360)

My budget is flexible, dependent on cost/benefit ratio (if I have to spend an extra hundred or two for significant advantage I will, and if I can save the same amount with relatively little loss in performance, I want to). But I plan the system to decently last at least 3 years without needing upgrades.

BTW, my monitor only supports 1280x1024, but I'm fine with that and I won't buy a new one in the next few years. I *do* like running things on max within that resolution though, and am especially biased towards having 4x AA turned on whenever damn possible! How can people even stand those jaggy edges anyways?

My primary questions are:

- Are all components balanced with no particular bottlenecking on any one part? If not, what would you substitute?
- Is everything technically compatible? (I'd feel like a real moron if I buy two pieces that can't work together!)
- Is the 460W PSU I have sufficient to power these components (and also 3 HDDs and DVD-RW)?
- I realize that at $700, the brand-new GTX 280 may seem like a horrible waste of money. But remember, my objective is a balanced system with no bottlenecks. If I opt for the 9800GX2 instead, I'll almost definitely need a new PSU as the GX2 is a power hog, and that's about $100 spent right there (if I'm wrong plz let me know). And anything weaker might result in the card being by far the weakest link for gaming compared to the CPU/RAM, something I want to avoid. But if it turns out I need a new PSU anyways, I'll be more friendly to the GX2 option. Unless of course you think both are an overkill, in that case please suggest something more suitable for the rest of the system!
- Comments on the manufacturer brands I chose?
- While I'm not a big sound connoiseur per se, I read that often buying a dedicated sound card results in FPS increase, due to offloading the work from the CPU. I can get a decent Creative card for about $50. Would it be more beneficial for FPS than spending that money elsewhere?
- Any other comments? All feedback welcome!

Thanks!