Previous amp/DAC was a hidiman ef2a with upgraded western electric tubes, I did really enjoy this and would definitely reccomend it, I preferred it over magni/modi combo.
If money is no object I would want an audio gd master 7 + cavalli liquid cobalt. The mjolnir I first hears was fee through a master 7 and it sold me on the MJ. The cobalt I have heard through another DAC that I cannot remember, but it was amazing, I preferred it to the liquid gold, though it was a very brief impression of both so take it with a grain of salt. I didn't really care for the bottle head crack I heard with the 500, and the audio gd compass was good but not mind blowing. I want to hear a bryston bha and a auralic Taurus, as I feel those could potentially be better than the mjolnir, though enough to justify the price increase, probably not.
I want to hear the darkvoice/la Figaro 337/339 from recommendations in this very thread, but I'm annoyed that as a dual mono design it doesn't have a balanced counterpart.
I haven't hears a mini-x myself but I would like to to see how it compares to the mjolnir.
Fwiw, I didn't really like the mjolnir with the hd800s, and some people disagree that the MJ pairs well with hifiman products, it is seen as an aggressive amp, personally I think the greatness of the he-500 is how it sits right on the threshold of warm/neutral so people can go with say a wa6 and get super luscious mids or my route of an MJ and get hard hitting transients and speed.