I believe that doing that will offer you a simple doubling up of your front channels. You won't have a way to independently control those channels without affecting the fronts that you already have set up -- and with which you are currently happy.
As someone else also mentioned, it may also drop the impedance "seen" by the amps, which could cause some problems (although I'm sure that receiver will go into protect mode before actualy failure). I wouldn't worry about this at all at low volumes, and if you run into lots of receiver shutdown, well, then you'll know what's up.
OTOH, you could give it a try and see if you like it. Seems like you're prone to experimentation, and it could be fun.
Another experiment you might do with those extra speaker outs is bi-amp your front speakers. I don't think this will be a true bi-amp because of the way the receiver is likely configured, but it might be fun to experiment with. It's likely that you will notice no difference, but if you have the extra speaker cable, you're out nothing anyway.
Good luck!