Let me use a theoretical for you.
What I see you saying is that if I buy a 1000w amp to replace a 1000w amp it should be a huge difference. That is crazy. In particular when if you had a 750w amp and bought a 1000w you wouldn' hear a difference.
Your ears aren't all that sensitive to volume differences. Takes doubling of power to get you anywhere. That all being said, you have an installation problem you NEED to fix. There is something wrong.
Not saying your amp isn't a piece of crap, but don't go buy a new one to HEAR something different. Bassink linked all budget amps as well so it isn't like you are jumping up into uber quality. So seriously, fix the install and REALLY determine what is happening before spending money. Be rather stupid to do it any other way.