Help me build a fine PC sound system

I’m looking for current suggestions to a great sounding desktop audio outfit which is pc driven or based completely.
!
Currently I’m using a Creative labs $50 USB sound card, and an Altec Lansing 2.1 desktop speaker system $200..

It really isn’t bad, and loads of fun. It allows me to play back lots of files & CDs I probably would not play too often on my main stereo.

So… I'm looking for recommendations of USB sound cards and a 2.1 speaker setup. Prefferably with both mechanical and software vol control, which will noticeably improve upon the aforementioned gear..

Noticeably.

What are your picks for:

USB sound card
2.1 speakers
2.0 speakers
Subwoofer

…… that will sound better than my above listed stuff? Actually it’s OK, but playing a setup disc it is easy to perceive how many areas of the bandwidth simply aren’t being honestly reproduced… but that’s about the only way to really highlight it’s shortcomings. Otherwise.. it’s well, fun…. And inexpensive.

Mainly the focus is for PC but if it will work with Macs too, that's great!. If it can integrate into a preamp or receiver or DAC too, that would be very nice, but not an absolutely necessary option.

Remember, the idea is a stand alone very, very nice sounding PC sound system first! It should be capable too of replaying file types from 16/44 to 24/192.

Do try to make the rig as inexpensive as is possible, so some reasonable and thoughtful blend of value to performance should be the real guideline.

I’m thinking too, as full range as is possible and likely a sub needs be in the mix… but nothing nutso.

Over achieving and high value items, front and center!

This might be fun…. Wadaya think?

Many thanks!