I used to record CMC8's direct mic-in into my iRiver h120- got some great recordings (acoustic/classical, but even so...). I never had to run all the way to the top of the levels; it's been a while now, but I think I was about halfway up the recording levels - certainly nowhere near maximum.
Biggest problem was keeping the mics far enough away from the hdd so that they didn't pick up the whirring noise from the unit; that might be a problem with a Tmic, but if they're designed for plugin power, the iRiver can certainly generate a decent enough recording IME.
FWIW.