Hello again-
If two UPA's is your plan, be sure to check with Emotiva and see if the UPA's can handle a 4 ohm load when bridged before you get them. Many amps have an 8 ohm minimum rating when bridged (because they effectively see only half the impedance). If they are not designed to handle low impednaces when bridged they will run very hot when driving your M&K's, possibly to the point of serious issues/thermal protection circuitry kicking in. That's why I suggested the more powerful stereo amp. You may want to see if the XPA's can handle 4 ohms bridged too; if they indeed can, you could get one now and use it in stereo, and another when funds permit for the switch to monoblocks.
Subs: check Hsu, SVS...other forum folks will probably make further suggestions.