The Mac has a single sound system, controlled by the single output volume control - you're asking for dual. I know what you mean about wanting to listen to two audio sources, but one way is to mute one while listening to the other, otherwise you simply get a confusion of noise. An example: I have iTunes playing music while I play Klondike with the card sounds muted.
Not all games enable muting though - I can't play Chopper and listen to iTunes simultaneously because the game doesn't allow muting. Some games might however enable lowering the game volume to to a minimum level.
And giving it 13 minutes between posts is a little impatient. As far as being a knowledgeable forum and has been known to be quick to answer problems, just give it a little more time as the person being the most knowledgeable in this field might not be logged on at this point in time.
Just a suggestion.
And as chas_m has posted a little more info will go a long way in getting a answer ..