Why not buy a used Mcintosh multichamp,the MC7106 would be a smoking amp for your rears & center,100x6 or 300x3,you can get one used on audiogon or ebay for about $1,500.
I owned the MC7106 for a few years & there arent many multichamps on the market that are as good as it was,especially for the used price.
But if your hearts set on other amps you wont have a problem running other amps along side the mac amp you have now.