Otari or Technics Reel-to-Reel ?

Changing from 1/4 track to 1/2 track will be quite expensive, but it will be a brand new head. When taking that, plus the fact tape is available one day and not the next, I think I'll leave the Otari 1/4 just as it is; although I don't believe there is any limit to improvement from widening tape heads, there is a limit to how much tape I can afford.

Orpheus10, I use IEC on the EQ and the medium setting on the Ref Flux.

I own an Otari MX-55N and it's a great machine. But the MTR-12's and 15's are even better, at least mechanically (fully professional studio machines). Also, the capstan needs to be
re-lubricated every so often by removing the "deck skin", This is accomplished after removing a great deal more than just the head cover. And it uses a special oil as well. It can be calibrated but you need test tapes. All fine and well. The thick manual goes on and on and on about special adjustments, features, options, etc.
A prosumer deck has no such requirements. You clean and demagnetize and that is IT. Of course i hate the plastic and the cheap off-the-shelf components.
And THAT was my whole point- I would want an relatively easy to use machine with an easy to understand manual, but using far-better parts made to last a much longer time under use and also sound quite a bit better as well. And i hate when people tell me that even a properly working Otari or Revox, Technics, etc. sounds like crap with the "stock electronics".
Name me one machine (not the one for over $20,000) that can fill in for a great turntable, or a similar CDP that plays SACD's. Anyway, i am working on just such a project (perhaps a modified Studer A810).

Albert's got Studer A810 with custom headblock for $25000. Must be a dream home machine.

you can get a Studer A-820 master recorder with additional outboard electronics for less than $25K. It's knowing how to maintain and professionally service these machines- or find someone who really knows what they're doing that can come over to your house. That (for me) presents the real challenge even if you have a large bank account.
Perhaps with the abundance of Teac decks on Ebay and elsewhere for sale, someone could improve upon THEIR parts-quality and put them out there for people with good hi-fi systems (like you and me). Akai, Technics, Revox, Sony, and others are also quite popular machines, and are now selling for a lot of money already, especially if they still work. Why can't a guy with an intimate knowledge of electronics upgrade them significantly beyond their original (read- 1980 Pioneer receiver quality) design? Anyone??