Preamps for Atma-Sphere OTL Amplifiers

I have a pair of M60 MKIII mono-OTL amps. I am currently using them with Atma-Spheres MP-3 pre. I'm looking for advice from people who are using preamps other than Atma-Sphere with Atma-Sphere amps.
Can't give you a specific recommendation, but based on my experience, you should limit your search to those with true balanced output.
I used the mk.IIIs with a CJ ACT2 for several months. Its an excellent single-ended preamp that matched nicely with the M60s, which did nothing to hide its character. Later sold it to buy an Atma-Sphere MP-1. I'll concur with Swampwalker on using a balanced preamp.

An ARC Ref3 could work well, but I haven't heard it with the M60s. Are there sonic issues that lead you to look for something different than your MP3?
I can't possibly imagine a better pre than an Atma-Sphere MP-1 or MP-3. I just went from a REF1 to an MP3 with my M60MkIII's. The switch was a revelation. You don't mention what options your Atma-Sphere gear has. If you don't have the Teflon coupling caps in both along with the regulator option in the MP-3, you might be better off with those upgrades for a sonic improvement. I should also mention that ultra low noise perfectly matched 12AU7's in the MP-3 along with low noise matched 6SN7's in V1 & V2 in the M60's will make an enormous improvement.
For what it's worth, there's a review at 6 moons that liked the MA-1's with a Shindo pre.
Mrderrick brings up a good point about the state of your amplifiers. I had my MA-1s upgraded with the Caddock resistors and output resistors, and it was a significant improvement. More natural sounding, less harsh. If you are looking to change to get a remote, Ralph has been talking about adding a remote capability to his top pre-amp (is that the MP3 or MP1?). It is a motorized device that will turn the knob. I saw a photo of it at a show someplace, maybe in the CES photos here. It looks like a Geneva wheel and motor mechanism, set up a bit like an old English grandfather clock between heavy plates. I don't have a lot of experinece with pre-amps and the Atmas. I haven't tried the Atma pres. The best I've heard in my system so far is the Pass X1, although I've been running a Wadia direct, which I preferred to any of the preamps I tried.
I have an S-30MkIII which is partnered with a Bent Audio remote control TVC. The combination is stunning with clarity, dynamics and imaging the best I have experienced.

However, the Atma's need a lot of voltage (4v I think) to achieve their full rated output so need very careful matching. My speakers are Avantgarde Duo Omegas which are 108dB/w efficient. I therefore don't have any problem with gain as I only require 1 or 2 watts.

In fact this combination works better in my system than the Atma MP-3 pre which gave so much gain that I had to remove 2 of the tubes and insert blanking plugs to reduce the gain. Even then I could only use a small rotation of the volume dial!
I have been employing an Aesthetix Calypso and Rhea with my MA-1 Silvers now for just short of four years and find them delightful. The detail, air, and greater level of volume control are all advantages of this choice. Atma-Sphere has more and better bass in my opinion with both the MP-3 and MP-1 than that of the Aesthetix but, that said, I have what I do based on priorities. The Aesthetix are fully balanced and offer single ended input as well for each input/output and a remote control, which is handy. They match exceptionally with Ralph's fine OTL's.

Happy Listening!
using an audiovalve rkv mark III otl headphone amp with my s30 mark iii, it sounds heavenly.
Having used other fine preamps with the M60s, I would use an MP-3 with the upgrades - which I now use, or upgrade to the MP1 which I assume must be better yet, but I have only heard it at shows, not in my system. What are you looking for that you feel you are not getting with the MP-3?
I have a S30 (among many other amps) and pair it with a Shindo Vosne-Romanee. Pairing sounds wonderful to me.
I use passive preamps with my S-30 for single ended mode. I run an Otari MX-5050 BII direct into the S-30 for balanced mode.
Joule-Electra LA-300ME or LA-150SE would be the excellent match !
Lately I've been using a YS Audio A2-SE with my S-30. It is virtually dead quiet in balanced operation. A strange, intriguing unit as it's still breaking in; will need to evaluate some more.
The LA-150SE was excellent, but I would not replace my MP-3 with it, I went back and forth for a few weeks with the two as linestages, no experience with phono, and thought the Atma/Atma combo was meant to be; but could easily have lived with the Joule, a wonderful preamp indeed, but a brief moment of sanity convinced me not to keep both.
Before upgrading to a fully loaded MP-1, I used a Plinius M8 and a Parasound JC-2. The Parasound was an especially good match with my MA-1's and I would have happily kept it if I didn't get a chance to hear a MP-1 in my system.

I have never heard the MP-3, so I can't say how it would compare to the JC-2.