Hodelrecords, it's good to hear your Fouriers are doing well. They are good sounding amps, maybe a bit on the dark side. The original power supply high voltage electrolytic caps were a brand called Binda, sourced from India, so it sounds as though the previous owner replaced them, probably a good thing.
I don't have any experience with CAT vs. OTL amps driving speakers like yours, but I am familiar with both driving Sound Lab ESLs. While I probably can't offer specific insight into which would do a better job driving big Avalons, I would generally recommend Atma-Sphere MA-2s as a minimum if you're going the OTL route; it may be only a matter of time before the Fouriers fail when driving loads that dip below 8 ohms. Avalon can give you an idea of the impedance. CAT amps should drive the speakers well; you'll have to audition them side by side with OTLs to see if you give up some transparency for the sake of control.
Brian
I don't have any experience with CAT vs. OTL amps driving speakers like yours, but I am familiar with both driving Sound Lab ESLs. While I probably can't offer specific insight into which would do a better job driving big Avalons, I would generally recommend Atma-Sphere MA-2s as a minimum if you're going the OTL route; it may be only a matter of time before the Fouriers fail when driving loads that dip below 8 ohms. Avalon can give you an idea of the impedance. CAT amps should drive the speakers well; you'll have to audition them side by side with OTLs to see if you give up some transparency for the sake of control.
Brian