I don't think a sound card is relevant - one doesn't normally expect hifi from PC sound.
If one wants hifi from a PC, it's no good expecting it from any internal sound card. There is far too much interference inside a PC. You need to get one of those external, usually USB attached, units. I have one here; a 96kHz 24-bit thing from Creative which cost about £150 I think.
I also can't tell any difference in the display quality between analog and digital, on my £400 CTX monitor. But that could just be having a decent video card; I can imagine that with others there might be a difference.
The thing is that for £400 for the lot, one isn't going to be expecting much. A decent reliable PC is about it.
I was very suprised the other day how slow XP pro is with 512MB RAM as opposed to 1GB. A vast difference - on the same machine.