I'd say that the Opera has a way better value then the A1 for as far as the options are concerned. The Opera has a DAC, a crossfeed, high and low gain and a pre-amp. It's also cheaper than the A1. Since the differences are fairly small sound wise except for the bass (assuming that the JensL describes this well // I have yet to hear the A1) I wouldn't bother getting the A1 unless I had way more money to spend than the Opera costs.
If you would want a DAC to do a $1300 amp justice you would be looking at a DA100, DAC1 etc. So to get a similar combo (like the Opera) you would have to start thinking about $2000 or more.
In my opinion the Opera might very well be one of the best amp/DAC combo's out there for the price. Especially if someone is looking for a all-in-one solution.
Edit: A small edit here. I just wanted to say that I really liked the review done by JensL. Thanks.