IME,
I've used an M500, as well as 160 stock, and Sank DX modded: if the 500 sounds good, and works well, keep it stock. I like the DX mods - they are actually quite bright, with that rich bottom, but a bit more hollow in the mids - not a bad thing, but the stock 500/160/260's seem to sound more forward in the mids, so depends on your desires for the particular application. I find the Beyer mic's circuit a bit noisier than modern equivalent's, but for non-ambient recording, it does the job fine...
If it were an option, I'd have one stock, and one for DX mod: the best of both worlds!
good luck!