I would go the opposite direction, and try to somehow borrow a better amplifier and hear what the system can do with it in the chain. If insignicant, great. If significant, try to find a really good deal on an amp to add to the system (cosmetically challenged amp, why not - who looks at a black box!).
Anyhow - good luck. You're assembly some high quality components, and you should be pretty set with your PC source.
Anyhow - good luck. You're assembly some high quality components, and you should be pretty set with your PC source.