That will work just fine. Anything that can add to the heat dissipation is good. I've even considered finned copper piping. Just keep in mind where the heat's going, because you don't want it to sit around in your case. Also, your PSU needs to stay cool too!
I'd be concerned with the Alu/copper combo, but after being put in my place about it, by Bill, I'd rather take the time to figure it all out, once and for all. (In other words, I'll refrain from comments
)