Otl's with AvantGarde Duos?

Nope, look into Lamm ML 1.1. Avantgarde's sing with Lamm's.

My semi useless two cents. You should really audition OTLs before going on reputation. They have a sonic signature which is hard to describe but most definitely present. I have horns but not Avant Garde everyone said use low power SETs the horns are so efficient. I didn't like the SET sound for the music I intended to play on that system. That being said I have heard OTLs which I thought were outstanding. I would be careful with the OTL and horn you may encounter a overkill and thus fatuiging upper register and a lack of good bass.

FWIW, we have lots of customers running Avant Gardes- Unos, Duos and Trios. One of the first reviews of the S-30 was on Unos. The combination definately works. Bass is of course no problem.

Naturally, since I am a manufaturer, you have to take any comments from me with a grain of salt. Your best shot in cases like this is always to go through the effort of audition. No amount of advice from others is really going to do it. You simply have to hear it for your own self.

Graham Tricker (GT Audio) design his own high end tube amps specifically for the AG horns (he is the Uk distributor for AG and he heled design the AG Model 5 amplifier).
With the AG horns, you need a really quiet amp with little noise. I've heard the TRONs at some length on several occasions. The background noise is silence with the AGs even with the volume turned up full using Trios. they sound great too.
Graham does have a US distributor, so you should be able to source a demo. If in doubt look at his web site (www.gtaudio.com) and email him.

I am an OTL fan. I settled on the Berning Siegfried amp with my Duos. They sound wonderful together. The Siegfried 811 amp is a SET/OTL, 10 wt/ch. To my mind it combines the intimacy of SET with the speed and transparency of OTL's. Highly recommended.