Elliot is correct, you need an amp with a loudness control, or at least tone controls, you lose a lot of music at the top and bottom end playing at low volume, it's just the way the ear works. Both those amps are great sounding, but will not make a dramatic difference in sound at low volume, and will not accomplish what you want.
Another solution is to add a small sub to what you have (there are many small powered subs now available that can fit almost anywhere), and try that first.