Although the OP has made his decision, for others interested in this application, the Mirage MM8 or its identical twin
Energy ESW-M8 are ideal companions for a 2-channel music-only system for mini-monitors.
I have a pair of the MM8s paired with some small towers (Mirage OMD-15) and they are wonderfully musical and have the speed, upper reach, and configuration controls to get a good blend with bass-shy minimonitors.
First of all, they are very quick, having a 1200 watt (peak) amp driving an aluminum cone driver with special high excursion surround.
Second, they are sealed enclosures with two passive radiators to provide some very controlled venting for more extreme excursions.
Third, they have 0-360 deg. phase control, volume, and crossover control (range of 50-250 Hz plus open-ended).
Put it all together and you can blend these little 9" cubes seamlessly with a wide variety of speakers, whether they just need some sub-50Hz oomph (as mine do) or fleshing out all the low bass for mini-monitors. One will work, but two are better, especially for larger rooms.
These originally marketed at $800 each and sound every penny of it. I got mine a year ago at the blowout price of $269 ea. Right now the MM8s are a bit more again, but you can get the Energy equivalent for $299. If you have a $500 budget for a single sub for music-only, come up with another $100 and get a pair of these. I'm listening and enjoying the hell out of my mm8-augmented system as I write this.