The Fishman system would be close to my last choice, next to magnetic
soundhole pickups
. Classicals are generally more suited to top
transducers like the K&K systems, or things like the Baggs Ibeam. Whatever
you use, a good preamp is a must.
If acoustic tone (unplugged) is a primary goal, classicals are not near as
generous as steel strings in thier tolerance to adding mass to the top. I've
had some success with the very low mass piezo film pickups (like PUTW), but
on a very fine classical just about any top addition can make a change.
Internal mics may be an option, but I've never heard one that I thought
sounded good on it's own.