i just recently purchased a rh910,i upgraded from an mzr3.yes,the headphone amp is apparently a little weak.my mzr3 has a separate audio line out(and a digital line out) which i would use to run the signal directly into my sony rcdw500 c cd recorder(stand alone) i dont use computers for any kind of music transfers.the new rh910 does not havea audio(stereo mini plug) line out just the line out to run it into a computer-whatever the plug is called.so.. i run a mini plug from the headphone jack into(the cord is a 1>2 type cord w/r stereo) two rca's into my cd recorder.sounds silly but it works out fine.if i monitor the recording while i am transfering it,it sounds a bit lower than when i listen to it on playback from the cd.it may just be from the recording level on the cd recorder,it havent looked into it too much since it seems to work out for me. the unit also has a 6 band digital eq which i can make some adjustments to the sound while transferring it.
as far as recoding lines.i have always used the mic in on my mzr3( i havent taped with he rh910 yet).make sure to adjust your levels manualy,DO NOT trust the unit to do it for you.i have had a few overly bassy and distorted recordings because of it.its a solid unit overall,as with most sony products.