generally speaking a good standalone preamp will sound better than using your mainstream avr as a preamp. similarly (and perhaps to expand on rar1's point), you'll likely get better sound with good standalone dac than using the digital ins on your avr. if you'd post your whole setup, your budget and your objectives, you'd likely get some good advise as to where to go from here.
Should I add a stereo preamp?
I have Paradigm S4 v1 speakers driven by Emotiva UPA-1 amps. I am currently using a Pioneer Elite VSX23. Would something like a Parasound 2100 improve 2 channel performance compared to the receiver? I am using a sub and everything is connected to the receiver digitally to avoid adc to dac for using the crossover.