Help me make sense of what I'm hearing

Help me make sense of what I'm hearing and steer me in the direction of the right gear.

This is long winded, so bear with me. A little background, this is my current setup:
CD-quality and hi-res flacs playback via linux MPD->optical "DAC Wow" dac->Adcom GFP-555II preamp->Golden Tube SE-40 amp->Kef Q300 bookshelf

Interconnects are Audioquest Diamondback, speaker cables are the Audioquest Midnight 3 Hyperlitz BI-WIRE.

This setup resolves acoustic and electric guitar/bass, upright bass, drums of kinds incredibly well for rock, jazz, blues. Most notable is the setup's ability to reproduce the punch of an upright bass (ex. Waltz for Debby and Christian McBride on Jimmy Smith's Angel Eyes CD) and electric bass (ex. any The Police albums). By punch I mean the natural volume swell (not compressed) - I could feel the bass in my chest without it sounding artificially flubby.

It only does a decent job on vocals and sounds very harsh on metal (ex. Metallica and Mastodon). The vocals don't sound as engaging as it could be and the metal guitars are so forward in the high mids that it's fatiguing to listen to.

Now to the point, I had chance to swap out only the dac for a Rega Dac and only the preamp for a YS Audio Plus-R tube pre. The Rega was polite in the bass and highs so the punch vanished but the metal guitars weren't fatiguing. The punch couldn't be regain by merely increasing the bass gain on the pre and the instruments were a little less resolving.

Next with DacWow back in place and the pre swapped out for the YS Audio, the instruments resolved well and the vocals were the sweetest I've ever heard - very engaging. The punch was kinda there but lower in volume - I can turn the volume up and hear the punch but the whole program was louder than I'm used to. As for the metal guitars, it was still harsh but more tolerable.

So here's the million dollar question: how do achieve it all (if not most of my goals) of punchy bass, sweet vocals, and resolving-ness without harshness?

Is it a different dac, a hybrid preamp, or cotton ear-plug (to filter out the harshness)? :-D

I brought up hybrid pre assuming that it's the best of both world: uncompressed and fast bass (solid-state) with a tube compression of the mids and highs?

Any help would be appreciated. Thanks.