Can I hook up sub directly to amp?

If your sub has a low pass filter and you do not want to run your mains full range, you should be able to go CD OUTput (not input) to sub to amp. Also many subs can run from the high level speaker outputs on your amp (essentially in parallel w your mains). Still haven't told us what sub you have. Also Vandersteen 2W and 2X can only run in parallel w your mains. There is a filter (aka crossover) that (in your case) would go between the CDP output and the amp input, and then both the mains and the sub get a speaker level connection to your ARC.

What sub?

My sub is an ERA sub10. Has inputs and output speaker binding posts as well as rca which I am using now which I will not be able to use if I buy the Bel Canto cd2.
Thanks for your help. I believe this to be a simple solution if you know what to do but I have received a myriad of answers, all different.

BelCanto - Sub10 - AR amp - Maggies.

In most cases, you can hook up from the speaker binding posts of your power amp to the speaker inputs of the subwoofer. Then, your speakers would be connected to the speaker outputs on your subwoofer.