My first build

Looks like you have the bases covered. I'll comment on your build, then throw some options at you.

You don't need 8 gigs of ram. 4 will be fine. The only people that need 8 gigs on a home comp are those doing large file manipulation. ie Video editing.

With that monitor, you won't use all of the 4870 1gb. So plan to upgrade the monitor before adding a second card. If you only go to 1680x1050, you won't need another card either.

If you are going to overclock, you'll want an aftermarket cooler. Sunbeam CCFP or Xigmatech 1283 are good choices.

Now, this is more philosophy, but why Intel C2Q? You're budgeting about $350 on the CPU and Mobo and when you need an upgrade, you'll have to build on a new platform. Granted the Q9550 should last a very long time. Now AMD just launched a new platform (AM3) that is backwards compatible with the AM2+ platform. AMD knows this is a very profitable way to build customer base and will continue to do that in the future. If you were to get a Phenom II x4 with DDR3 ram, you will find performance to be on par with the Q9550. But when the next gen AMD processors come out, AM4 we'll call it, they will most likely support the next ram standard and DDR3. So you'll already have the ram and won't have to buy any more. Plus the new next CPUs may work in the motherboard too just like AM3s can fit in AM2+ boards. DDR3 ram is only $10 more than what you have spec'd out for DDR2.

For comparision, AMD x4 945, 790FX mobo, and the 4870 1 gb for $410 vs the $500+ on the intel side.
http://www.newegg.com/Product/ComboDealDetails.aspx?Ite...
Save money and the 790FX will support 2x vid cards better than the P45 because the PCIe slots run at x16/x16 and don't get split into x8/x8 like the P45.

Something to think about. The Phenom IIs OC just as well as the C2Qs

And don't forget a HDD.