I don't have any recommendations for actual dvd running software however if you enjoy movies and collecting you'll probably enjoy using http://www.dvdprofiler.com It's a very nifty program for categorizing your dvds...assuming you don't already have it.
If you aren't going to be using spdif (5.1 surround sound), then the software that comes with the system is a great suite. WinDVD is what comes with it, and it's pretty darn nice. I personally like Asustek dvd, but it's hard to find and it's just a modification of powerdvd I think. Hope that helps!