Cheap upgrade path?

I did not like MSB. It has overemphasized mids with unreal brightness. Listening fatigue guaranteed in 10 min.
There is nothing wrong with older DACs. They're more musical and natural. Try used EAD DSP7000 it's on sale here from time to time for <=$300 and find where the music is.
Unfortunately I've never heard Muse.

A third path is to pick up a used Link or Link II and send to to Stan Warren or Dan Wright for modification.

I have the newer Muse (the model 296) and it is unbelievably good. It seems to me if you can get a used model 2 (make sure it has the besel filter option which is VERY important and HDCD - if you have HDCDs) or a model 2+ (the same thing but with all the options). The MSBs are not nearly as well built or designed and Muse digital gear has a palpability like analogue. The 2+ was a reference quality DAC 4 years ago, the MSB never was nor will be. Now if you could afford a good deal on a Model 296 ($1250- $1500) you'd really be in heaven.

Good Luck.