I'd like to add a different use case for such amplifier - home theater PCs, such as those running Windows XP/Vista Media Center Edition.

Such setups usually run in the living room, with full-size 5.1/7.1 speakers, so it's different from what you originally envisioned. The missing part for an audiophile is the amplifier optimized for PC as the only source (no need for signal switching). Today the only offering is the line from Simplifi Digital http://www.simplifidigital.com/shopsimplifi/amplifiers-usb-input-amplifiers-c-2_6.html , which is what I have, connected to Axiom M3s front, VP100 center, QS4 in the back and EP175.