I have a Pioneer elite 81TXV and a set of boston Vr975's for front speakers. I have a set of NHT and a set of Klipsch to complets the 7.1 package. There is only one subwoofer connection on the reciever so I have a monster 300 connect daisy chained (incorrect terminology) to both of the VR975 powered subs. I just recently aquired a boston VR500 subwoofer and have no clue on how to wire this configuration. Please help.

Use Y-splitters

Don't daisy chain, even if your sub does have an unfiltered pre-out.

BTW, now that you have a dedicated subwoofer, you may want to consider NOT separately wiring your 975's "subs" to your receiver's subwoofer output. This is personal preference, and you should experiment, but things can get complicated on the low-end when you have both your powered towers' "subs" as well a dedicated sub connected to a receiver's subwoofer output. You have several different connection options.

Def Tech powered tower owners face similar issues.