My new band uses IEMs exclusively, so I'll chime in and say this:
The IEM unit you're using, while important, is FAR less important than what's going into it.
A fully customized monitor mix going into a budget, wired system like that Elite Core will be way better than a haphazard mix that you have no control of, into an expensive IEM wireless system.
We're using a splitter snake, running everything onstage (drums, guitars, vocals) into a AH Mixwizard 16 channel board. Every band member has full control over what they hear in their in-ears.
Even WITH my nice $1000 Sennheiser G3 IEM system, it still sounded like **** - until I messed with mics, mic placement, EQ, and levels, on the board. It took hours of experimenting to get my IEMs sounding big, full, and natural, and not *feeling* like I'm in a fishbowl. (And I'm still tweaking, every show...)