Isn't there any kind of impedance mismatch between the recorder's output (designed to go to a line level device) and the guitar amp's input (designed to accept a signal from a guitar p/u)?
I've never bothered to try this thru fear of the above being a relevant issue.
It's possible to reamp from a mixer. I'm sure the results are better from a dedicated box designed to match impedence. But this shouldn't stop you from experimenting! When sending a signal from a mixer to a amp or effect, just watch your level coming from the mixer. Keep the level going out low and the amp/effect that exspects a higher impedance won't really mind.