I hooked it up using the tape loop just now. Might be placebo or conf bias or whatever its called. It just sounds SLIGHTLY less dynamic. which is one of the wa2's strong suits i always thought. Sounds like i loose a tiny bit of detail and space in the lower frequencies as well. but it could very well all be in my head.
i don't know enough about the circuitry of the marantz 2270 to know what all the tape loop runs through before being spit out.