I have and between the (2) I would take, and did opt for, the 306 Pro, aside from its better sound, you don't have to give up your CDP/SACD player in the exchange.
I ripped my whole collection of Redbooks and listen to the Apple lossless files 85% of the time, but, in the end, the actual discs do sound a wee bit better, so once in a while, I prefer to play the disc. While, I only have a collection of (4) SACDs, its fun to play them too once in a while.
There may be DACs that compare favorably or even beat out the Cary 306, but against the Benchmark its a no brainier to go with the Cary - assuming you like their sound in the first place...
Good Luck, John