Very good, Troy; the MRX500 should serve you well.
Using the "more gas in the tank" attempted analogy though, indicates that you may not be grasping the concept. A car doesn't run any better with ten gallons in the tank than with one. If the tank was completely empty, then there's a difference. If the amplifier in the receiver can supply enough voltage for the needed volume, there's no benefit in buying another unit with a higher voltage supply which would just sit there partly unused.
Ok a little off on that analogy. How about My Hyundai Sonata is a great car. I can drive from Bridgewater to Halifax easily everyday. However, I like to go a little bit faster and some of the hills are quite steep, so my car stuggles. It keeps the speed up buy sputters and I don't quite have the spped at 70 mph only 50 mph and I want to go 70 mph.
Then one day, I am passing a sports car and I am at 70 mph, however as I top a crest a car is coming in the other lane towards me. I have to floor it to get by and out of the way, but hey my car dies at 80 mph and sputters and well we know the result. Either I crash or let my foot off and put the breaks on and pull back in behind the car I was passing.