I can... but fully expected you to stick with your 5.1 preference!
I was very happy with my Creative T40 speakers (and still use them with my TV). Maybe they're not *quite* as punchy as a subwoofer is, but they're pretty solid in the bass
IMO and better all round. Question is, do you want quality? If so, investing the money in 2 speakers will always be better than investing it in 6. If you're desperate to have surround sound, then obviously you're better off with the 5.1. But when I switched, I really didn't miss them - at all. And losing the wires was a very welcome relief.
As I said, the amplifier route is much better - I took a Marantz PM-32 and a pair of Tannoy Saturn S30 speakers off g8ina's hands for nothing, and they blew away everything else I've tried with my PC. It's no surprise though, when you think that the cones are about a hand-width in diameter compared to the typical 2" in PC 5.1 systems. Obviously to go out and buy new it's not really a fair comparison, as it would cost a huge amount, but you can get a heck of a lot of quality for very, very little - and it just proves how poor "PC speakers" are by comparison when you can shell out £100+ for something inferior to a 20 year old Hifi set.