A couple of easy things you can do to address the situation - "the treble is shrill to my ears and the bass not as clear/punchy as I prefer".
1. Move the speakers farther apart and toe them out a little. This can reduce the treble shrill, and has worked for me.
2. Check your speaker cables. I have found that low gauge copper speaker cables improve the bass, thus, reducing the emphasis on Treble... Try "WORLDS BEST CABLES - 7 AWG - Ultra-Pure OFC" on amazon. You can very easily return them for your money back if they do not help your situation. I got a lot more bass out of my speakers with these exact cables.