I don't see the point of using MicX with TMX, which is pretty darn fine-grained to begin with...(posted 9061 days ago)I used to use MicX 1:3 for my Minox APX 100 negatives, and it was a mixed bag. The grain was EXCELLENT - virtually invisible in a 4x5 print viewed from anything beyond a few inches - but... The negatives were flat and very lacking in contrast; I ended up printing nearly everything with a #4 filter. And, while I never noticed "loss in film speed" or "compromised sharpness due to dissolving grains" (both common problems attibuted to MicX), I had another issue: serious amounts of crud in the solution that adhered to the negatives (undissolved developer grains, dust, sludge, etc.) Great prints were frequently nearly ruined by nasty schmutz in exactly the worst place. (And no, I never had these crud problems with D-76 or other soups.) I also found the shelf-life of even a half-package was too short to get more than 4 or 5 rolls of Minox film - which only require about an ounce of stock solution each - out of before having to toss it away.
Anyway, I've run TMX in both good old D-76 1:1 and Xtol 1:1. (No, I haven't tried the T-Max developer.) Results in the D-76 are very good (even with Minox negatives) but tend to be a bit contrasty, and there are sometimes those problems with blown-out highlights and/or blocked- up shadows. Xtol tames the contrast and gives even better grain, but I keep borderline-underdeveloping and getting thin negatives where the fogged ends aren't totally opaque. (Now mind you, for the Minox negatives, I am agitating far less than recommended and adding more dev time to compensate - as agitation promotes visible grain, and that's the main enemy in Minox terms - but I haven't hit on the right formula just yet.)
Anyway, I think Xtol is probably the way to go for TMX, especially in formats larger than Minox where there's some maneuvering room in terms of grain/sharpness/contrast tradeoffs. But you know, that old stand-by D-76 1:1 is pretty darn good too...