Class D options

Merrill Audio is another great option... Tons of online reviews. 

Why not buy a new amp the day after your tube gear fails? Are you far from an urban area or hifi stores? You can also buy all of these items on A'Gon from online dealers. I was considering the Mola and Theta and found a few dealers and private sellers here on A'Gon that sold them online. 

I just bought the Benchmark AHB2 amp and a DAC3L online.  BTW - I went with the AHB2 over the Theta and Mola based only on reviews. 

I suspect much of the issue with the Mola Mola Kalugas is that many reviewers and owners don't give them a chance for break-in.  They are superbly engineered amps but the break-in is supposed to be really severe on some class-D....I have heard to expect changes up to 1500 hours.  

Red Dragon audio monos ... 

+1 Bel Canto REF600M, but you should consider the Bel Canto Black EX amp. What if you like it better than your tube amp?