I bought a MC3+USB to convert USB to coax. It works great. I picked up a LHY OCK2 clock for cheap, at some point I'd like to try the Nano.
I have my TV in it's TOS input and that probably was the most noticeable improvement.
My CD transport has a 10m clock Input also. I thought it was a worthwhile upgrade.
Unfortunately you can't demo these units, they are special order and not returnable through dealers. Once in a while one will pop up at TMR. If i were to try a Nano it would be a used one through them as they have a great return policy.