As said above, in that price range, you will not notice an audible differance
in sound tones on low cost receivers. Your best bet is to sell your speakers, buy some that are not know to be edgy. Next, spend some time with room acoustics (maybe should be tried first). After that, and you are not satisfied, go out and spen between 500.00 and 5000.00 for a warm sounding amp.
Your best bet is to play with room acoustices then buy new speaks, then last, new amp (in that order).