If you are looking for "ultimate "in redbook as well as SACD plyaback then there is only one company that can deliver--dCS--the Verdi SACD transport, Purcell upsampler with DSD, Elgar plus. Absolutely the best! IMO anyway. I wish I could afford them though, as it will set you back 30 grand.
Meitner and dCS are both top choices. I would add to the list Muse Model Ten transport and Model 192 DAC with DB25 connection. Substantially less money than either Meitner or dCS and will hold their own against them both!
I know the Theta very well and compared it to 3 other players. The Muse Ten with an attenuator module was the better of all three. It was more musical and had better mid-bass and overall soundstage. The Muse offered specificity and dynamics that I have yet to hear with any other player.