First of all, welcome to HWC! The only thing that I would change if it was my build is drop the sound card for now and invest more in the video card (4870). You can always add a sound card at a later date if you decide you really want it (there are some threads here that suggest that there are better ones for a lot less).
I don't know if you plan on overclocking, if you do, check to see what the build warranty will cover. I tend to think that you will find it more rewarding to build it yourself and rely on manufacturer's warranties for your components. In the end, it really depends on what exactly the build warranty will cover. If it is only labor and trouble shooting, then I would doubt that it is worth it. There's a lot of troubleshooting knowledge right here at ol' HWC.
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Asrock Z68 Extreme3 Gen3 - Intel i5 2550K @ 3.4 GHz - Corsair H80 CPU Cooler- 4x4 GB G.Skill Ares DDR3 1600 - EVGA GTX560 Ti
1x120 GB Mushkin Chronos Enhanced SSD - 1x500 GB Seagate Hybrid Momentus - 2x500 GB Seagate Barracuda 7200.11 - Pioneer DVR-212D - Antec P182 - Corsair TX650 - 22" Hanns-G - Windows 7 Pro 64 SP1
The world is your oyster. Shuck away my friend, shuck away!