For the best price and quality your best bet for a amp is (drum roll) a Pyle Blue Wave Amp. For the price you pay for on one of these amps you are actually getting better than what you pay for. I always thought those were shitty products. Pyle, Legacy, Pyramid, and Lanzar. They are just way too cheap to be a reasonable amp and sub. These products are pretty much made by the same engineers. You would expect to get really shitty quality from a Pyle for the price you pay but actually you get good quality for what you pay for. Of course, you don't get quality equal to Rockford Fosgate, JL Audio, etc. but price vs. quality you're getting a good deal. Me truthfully, it's hard to believe that's true but this is a matter of car audio engineers opinion.
the big problem with those cheaper products is durability and design. they don't hold up very well.. when they work sure they get loud, but not the cleanest products, and made cheaply. Look at the failure rates. Sony is a good example of this.. look at all of the problem posts on here. Most are Sony, Boss, Pyramid, etc. If they are higher end stuff, most times it's user error, or someone trying to figure out a feature more than something flat out taking a dump on them.