Concrete Floor

It could be fun to push your stack back and use the entire garage as a bass enclosure (especially putting it diagonally in back corner).

Not having seen the actual situation, I can't really say much except try it in various places. Deflecting your sound off of concrete is never fun. I've put a rug under my rig but it was really there to keep my pedals from traveling on the concrete.

 

kinda thinking out loud, but,

i would think a concrete floor would mute the lower tones and just be really reflective. take it off the casters and put both cabs on the floor. the 2x10 might add a little more bass response with it on the floor.

 

When I play on a concrete floor I boost the low mids, it sounds like a little too much by itself, but to me it sounds really nice and punchy once the guitars and drums get going.