MB Quart quality has gone down after maxxsonics took over. I have seen many bad comments about poor quality of even Q series amps, which are supposed to be MB Quart's premium line. If I was buying a budget mono block amp, I would buy a Boston Acoustics GTA mono block. They have very good review from pasmag, (very good measurements of power, thd, efficiency). They also have a parametric bass equalizer to boot.
This comment goes contrary to what I have done recently, which is to buy MB Quart amps, but I took that risk because I got very good one time discounts. Without those discounts I'd go with Alpine, BA, Kicker, etc.