I really believe some better subs will do more than you think. I don't think another amp is going to offer you much, likely nothing. You need to double your power for any significant gains, and by that I mean you only gain 3 dB of volume by doubling your amp power. You'll be able to hit slightly higher volumes cleanly but it will not affect the actual sound quality.
Clean, effortless bass however, can clean up the whole range from top to bottom. I know that's not intuitive but dirty bass has a way of coloring the whole performance in ways you don't pick up on until it's gone. We don't hear distortion in lower frequencies as obviously as we do in the higher ones, but it can affect the overall sound. Once you experience it you get it.