Better speakers are the usual route to better sound quality. What distance are you from the speakers?
The avr upgrade to a 3800 will at least give you pre-outs so you can use a more powerful amp if needed, plus some other nice features the 1400 doesn't have. The Emotiva Basx line of amps are not much more powerful than many avrs' amp sections, wouldn't bother with them. I'd first figure out speakers, tho.