There are really good speakers that have bulk prices, get discounts the more pairs you get.
This is one is really good.
I had the same problem. There are good 2 speaker systems for PC, but no good 5.1 anymore.
I sort of solved the problem of 'high end' 5.1 pc sets after finding the Monoprice 10565 5.1 surround system for $220. They do need an av receiver/amplifier (another $200) but they seem to be an option for "high end' PC solutions.