I still have pretty crappy mains, but a VP150 for a center. It produces better base than my Sony floor-standers.
If your receiver is setting the VP150 to cross at 100 Hz, it may be because of positioning. It's -3 dB point is 85 Hz, so it should be able to go lower. How do you have your VP150 placed?
Also my receiver is limited to a single, global crossover setting, so all my speakers are at 80 Hz. My QS8s seem to do fine. The auto-EQing of the receiver did bump them up a tad toward the bottom end. They're already down 3 dB by 95 Hz, so setting of around 100 Hz is pretty well suited to them.
