I have tried Axioms EP350v2 and v3, EP400 and EP600, SVS PB12-nsd, my current PB13 Ultra and my old under powered D-box 10" sub with my M22s and they all have blended very well, most subs are easy to blend with speakers, the PB12 - nsd was the only one that I felt was a little overpowering but that was due to the subs FR and nothing to do with the M22s.

Almost forgot, the Paradigm DSP3100 was another incredible little sub for the money and worked very well with the M22s and even my M80s.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70