I can do better than your current list, I'm sure . . . give me a while and I'll post again with a build.
Oh, and onboard sound is usually fine, but for gaming or serious audio use, it's really not.
Edit: OK, here's the build. bear in mind this is without a monitor, OS or mouse/keyboard . . . I would guess you have the first and last, not sure if you have a legal OS disk somewhere, otherwise add at least £50.
CasePSUSound cardDVD burnerGraphics cardRAMCPUHDDMotherboardCompared to the rig you put together, this has a PSU and sound card, also a better graphics card.
The RAM is faster and from the UK rather than US too.
However, some may say the case is not as good (personally I love this case, it's deceptively cheap), and it does have a slower CPU.
Finally, it's also cheaper, at £343.98 excluding delivery.
Hope this helps somewhat.