The Sennheiser headsets sound better than the Shures. If you're moving around a lot near the speaker system, double check the mic model that comes in the kit and verify if its Omnidirectional or cardioid. Omni can be a problem more so than cardioid.
I tried to use a Wireless Lav (clip on) system with a Bose L1 system. (180 deg coverage with the L1's)
It was not usable with an Omni Lav mic.
That's when I discovered most Lav and headset kits were usually Omni and if you order you can order it with the Cardioid mic instead.
MegaBass head, SWR 210, Trace 115, Ibanez RB999, 27" Imac I7, Onyx 1640I, Motu Ultralite