Hi Mark,
Given the impedance issues with ML speakers, the consensus is that an AVR is likely not up to the task of driving the speaker.
Given the fact that the Source was designed for folks who wish to use an AVR, you may be happy with a different AVR.
Most folks will tell you to use the AVR as a preamp only, and to use the amp outputs to drive a dedicated amplifier, if you want to optimize performance.
You may want to consider Outlaw electronics. Big bang for the buck. Other on line choices are also available.
And, of course, there's always Audiogon regarding used gear.
Good luck.
GG
PS: If you want to buy an AVR and be happy with the results, I suggest you check out Arcam.