TF2 uses whatever the default sound device is in windows, you can't set TF2 to play though a specific device via the options panel.
 
Not sure if there is any sort of command in the game itself, but you could try configuring your sound cards output, dependant on how much control you have on it. only alternative is to buy an ipod etc.
 
mute the music in tf2 and use your pc speakers for the game sound (shooting, talking, etc)
use your stereo set (or any other device) to play music
no need for earbuds
 
If you're gonna use earbuds for gaming you might as well just buy a headset. Other than that i have no idea how to do it on 2 seperate devices
 
Lol, Linux through Wine can actually do this sorta shit. You can listen to TF2 on your headphones or TV, and micspam through your TV or headset.

But only if it's Digital/Analog, because I think it's impossible to separate 2 different sounds through the same output device.