A couple of quirks to note about the Rumble 100:
- The FX Return comes
after all of the controls, so plugging into it effectively bypasses them. This includes the Master volume, so you'll need to adjust the output level of the Opus if you want to change the stage volume
- The XLR Line Out has a permanent cab sim applied to it, so if you want to send a DI signal to the desk, you'll definitely need to take it from the Opus
I don't own one any more, but as I recall they're quite "voiced". i.e. low cut, high cut, and mid scoop. I imagine you're likely to get a better result from the Electro-Voice, given that it aims to be comparatively neutral/flat/uncoloured.
Also, given that this is a QSC thread - consider the QSC CP12, as recommended in the OP and only 50 bucks more than the EV