Amp pairing for Sierra 2 bookshelves and Vtf-1 Mk2

Also I know class D doesn't mean tube but I've heard they sound similar.

I would like two add my two cents.
I currently own a pair of Sierras but they are version 1with the SEAS silk domes tweeter. I bought them dirt cheap of Audiogon and put them in my main system while I finish up a pair of DYI speakers I am building. Currently they are paired with an Exposure 3010s2 stereo amp and Light Speed Attenuator preamp from Tortuga Audio (Used $1600 total), and a Schiit bitfrost dac. The sound is fantastic. Smooth, fast, thumping, with an excellent sound stage. The thing I like best about this system is that when I put on sub par source material the system is forgiving and still very musical.
I have been down your route trying out amps from $400 to $5600 dollars. Just rotated out a Hegel 300. The best advise I can give is find something musical especially if you are on a budget. My experience with Class D amps and treble has not been that stellar. Hypex (not the Ncores) Class D, Nuforce, and ICE power modules all great amps but there not gonna nock your sox off if your looking to get the most out of those RAAL tweeters. I have heard only one exception, there is a DYI amp fully assembled on Amazon it's the
SMSL SA-36A Pro 20WPC TPA3118D2...and its $70 bucks, it has the best treble of any digital based amp I have heard. Besides being limited by its power factor it also has some of the most refined midrange (vocals) I have also heard in my home.
What are your musical tastes?
I have tried or owned a lot of the amps you will be looking at:

Hmm well that's worrisome as I just ordered a Virtue One.3 but for the sake of future upgrades I listen to a wide variety of music. Hip-Hop, Krautrock, Jazz, Electronic, Folk, Punk, Prog-Rock, among other things. I've heard the ONE.3 is comparable to the Nuforce IA 7 V2 so if you've heard that you have an idea of what my system will sound like. I would say that I love mids and highs so the treble news is saddening.

Fear not Jemidy

I also had the Virtue Sensation M901 which is the bigger brother of the One amps.I recall the sound as being smooth, and tonally rich. The amp boogied and had tighter bass than the Nad I had before it. The only thing I didn't like was the sound stage was some what narrowed, but I later found out that was probably due to the older tubes I had installed in the Dodd tube buffer.

Good to hear any recommendations as far as preamps go in the >$500 range? I was going to go with the Schiit SYS passive pre but with your experience you might know something better!