I remember in the late 80's my buddy had 2 12 inch pyle drivers in the back of a Chevrolet Corsica running off of a 300 Unic amp that out performed the Punch 300 and 650. Unic was as cheap a swap meet brand that you can find back then. The same theory holds true today. If you get a decent well built amp, good speakers and also a good head unit, you cannot hear the difference between brands. A lot of car audio businesses are functioning off of that premise today. gunz4me a lot of the same amps built in Asian buildhouse will not be existence 10-20 years from now because more and more people will get tired of those cheaply built amps. The better quality amps will last longer because they are built with better quality components and have better crossover sections built in them, etc. Good brands to look into are Sundown, Alpine, Atomic, MTX, Kicker, etc.
Wasting your money on the premise that different amps have different sounds is what keeps these car audio companies in business. A person that really believes in the differences should get their picture put up on the "sucker of the month" wall in the sales sections of the car audio companies.
The smarter guys such as N2Audio, gunz4me, RFvega and others just sit and look at all the fools on different car audio forums trade and sell their amps on the premise that there is something that will sound better out there. Find a brand that you believe in and stick with it.