Probably a stupid question, I don't see many potential issues, but I have a Line 6 Floor Pod and an old stereo I recently picked up. At the moment, I don't have an amplifier, but I was thinking of buying a dual 1/4" to RCA adapter to connect to the amp for the stereo. It has 15 inch speakers and horns and such, so I am expecting it to sound great. The pedal sounds good through headphones, but would it possibly not sound so good going through an old stereo? It's an old tube head, so I assume it'd be just like playing through a guitar amp, but with better sound quality thanks to the stereo connection.
Should sound fine. If you have a subwoofer unplug it; lone guitar signals don’t sound good dumped into a sub.
Absolutely it will work. If you get a mixer then you can mix your guitar with whatever you are playing on your stereo. Plus add a mic and whatever else you want. If you have a "Tape Monitor" selection like many old stereos do, then put the mixer in the tape loop. If not but have a pre-amp to power amp jumper on the stereo you can put the mixer there.