I think you're sorta asking the wrong question, so I will spin it differently. For sound quality impact it's best to find an amp that has the best synergy with your speakers - so I'd focus squarely on the amp over the preamp but not just any outstanding amp but the one that allows music to flow the best from YOUR speakers. This may not have anything to do with spending the most you can afford....it's about finding synergy. My speakers sound best from a tube SET topology with a bit of wattage headroom. I could have spent 3X on a higher end push-pull amp and it wouldn't sound anywhere close as good as what I have.
