Citaat:

I'm using the cheapest of the cheap. Everything I have is very low end.




That may be. But your productions are top notch!
In the end it is not what you have but how you use your gear that makes the difference.

Should your amp (after Mac's sugestion) really need to be replaced, you might want to try selling your bookshelf speakers and go for a set of powered studio monitors. There a lots enough monitors available at $100 a piece (most monitors are sold per piece but there are that are sold as a set).