decooney,
I have had a DS1, D2, and his latest preamp, the Raven, but needed to part with Don's 300b monos so I sold the Raven in a combo deal. Each preamp version has improved SQ, but I also had a stock Tube4Hifi SP-14 at the same time in my bedroom system and it was stellar performer, purchased used for $1100. With Roy Mottram's upgrades, I'd guess the new V23-K1 is quite close in performance to the DS2 and I would have bought it but for the used DS2 I found for sale. I was looking at the Supratek preamps but as far I could tell, they are all two-box units that would not fit in my rack.
The OP has gotten some excellent recommendations to guide his purchasing decisions. This forum is a wonderful source of information.