I don't have direct experience with that Onkyo, but it's my understanding that it has a pretty substantial power supply. I do have direct experience with the M7si. I have lived with a pair of M5si's for 15 years, and also put together an HT system for a co-worker back in the mid-'90s, which included a pair of M7si's for the L-R speakers. I installed and tuned her system. The Msi-series Mirages like a lot power and current. The Onkyo isn't the biggest and best beast for that, but it's a better start on a shoestring than many other options. The great thing about the M7si's is that they will reward you for any improvements you make upstream, whether that's better amp, better cabling, and bi-wiring or bi-amping the speakers.
I say go with it and bi-wire the speakers right away if you can. Feed the woofers at least a 12- or 10-gauge speaker cable.
I say go with it and bi-wire the speakers right away if you can. Feed the woofers at least a 12- or 10-gauge speaker cable.