Lavry is the flavor of the month. Their 'Blue' series is the latest rage and, by all accounts, it doesn't disappoint. I have yet to hear them personally, but I know a guy in Nashville, TN that I could hook you up with to discuss them.
http://www.lavryengineering.com/
I personally use a Benchmark DAC-1 and it's the best at removing jitter in the D/A conversion process. They're coming out with an A/D (with a build-in preamp) soon, too.
http://www.benchmarkmedia.com
There's also Crane Song, Apogee, Lucid, Mytek, blah, blah, blah, ..... and the list goes on.
You may want to check out Gearslutz.com if you really want to know about D/A or A/D converters. The forum's kind of geared towards this kind of stuff. It's moderated by some very, very accomplished producers and engineers and mastering engineers.
It's run by Julian Standen (The Library Studio) in London.
Here's a good site that does a lot of comparisons ... I don't know if they use a variety of converters, but it's a great resource with audio files comparing preamps, mics, (and hopefully converters)...
http://www.thelisteningsessions.com
There's not much difference among the high-end converters. It's more subjective based on you monitoring environment. Without a doubt, you will appreciate a good converter because your audio will absolutely 'open up.' They're the most important link in the signal chain (besides the monitors).