When I purchased my Tact 2.2x, I also had a ModWright Sig.2 P-3A/Monolithic, and I compared it to the DAC inside the Tact. The Tact DAC was a little 'cleaner' with more detail, but the PT had better bloom and decay. Same league, though, decision based on preferences. But the addition of Tact room correction was a revelation in my system (and I have a dedicated room). Room correction with the Tact DAC was miles ahead of using my Dodson DAC without it.
However, it was when I changed amps to the Tact amp (replacing a Gamut), keeping the signal digital all the way, that I felt I crossed the point of no return. The Tact 2150 is a great DAC, and quite a good amp, too. Tact is now including room correction with their new amps, and if you don't need or plan to use subs or digital crossovers, I would seriously recommend you look into this option. At the price, it's a steal: digital preamp, DAC, amp and room correction all in one reasonably inexpensive box. All you need is a transport (or squeezebox).
I haven't used the Tact with tube amps so I can't comment here, but I no longer miss my previous tube preamp; nor have I compared the later DSP with the old one, but a friend who owned both thinks the 2.2x (and hence the 2.0s) sounded much better than the 2.0.
Good luck with your decision.