I wouldn't use the 10 Ga solid simply because it is difficult to impossible to route. I agree with everyone else about the cost/performance on Monster.
Personally, I use 16 Ga stranded line cord on 15-20' runs from an Onkyo 806 to Klipsch KG-4 mains. I have measured with an oscilloscope and done an FFT which shows no frequency dropoff in that distance.
If you want to be safe and go a bit upscale, look at 12 or 14 Ga from Monoprice.
BTW, I use a combination of spade lugs at the speakers and dual banana plugs at the receiver for termination. It really helps in keeping the ends clean when re-organizing cables.