Glad to hear you like it! You are using it as a headphone amp only as of right now, right? As I have said it works well as a headphone amp with Grado's and is supposed to do well with low to mid impedance cans and it sounds like it's doing well with your cans. I've compared it's headphone amp capability to my Mapletree tube headphone amp and Zhaolu discrete headphone amp. Either of those amps outperforms the Musiland's internal amp, especially the Mapletree, with my Grado HF-1 but that shouldn't be surprising really. It does surprisingly well but it is a tad bit more compressed and less separated sounding than the other two, among other little differences of course. Now, the Musiland used purely as a DAC (not driving headphones) with my Mapletree amp or even the Zhaolu discrete amp (the Zhaolu has a convenient analog input to it's amp) and it's noticeably better than using it as a DAC/amp combo. I still think the Musliand performs right up there with my Zhaolu 2.5C, it's an excellent DAC, which I've gone into some detail in other threads. It reminds me of the 2.5C and they both use the CS4398 DAC chip.
I think the MD10 did clean up some and opened up a bit more with a good 100 hours on it.