Welcome Patrique!

My thought would be to go with the 60s and a 500 for the sub...holding off on the two back channels. Many find that there's not a very big difference between 5.1 and 7.1 (though that's room dependent) and, in either case, you could choose to add two more speakers later if you feel something is lacking.
::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::