I wouldn't call the Delta pro - the converters are definitely not pro, also the word clock jitter is too high to pass in that category.
I'd call it "bedroom professional" meaning that it is close to pretty much the other interfaces out there like the Presonus Firepod and the Edirol.
You can achieve good results with it and I've heard some good demos done on it. It is all matter of knowing your equipment and good ear as an engineer.
From what I remember I think it had a spdif input/output so maybe you can also match it with a good preamp that can feed via spdif to bypass the converters when you need that extra fairy dust magic for vocals.