I haven't heard the 500s, but they are intended to be used with a THX processor. IMO, the 900s are very similar, using the same drivers but different crossovers, and cost less.
Here is a link to the AH 12K recommended system which uses the 900 series, and IMO, would be an excellent setup.
I've also installed a 904/905/903 setup for one customer and it sounded pretty amazing for the price.