I am seriously looking into soundcards at the moment, 'coz a lot of people have asked me what I think of this and what I think of that - and I simply do not know - I have never used any - so I have asked some people who design things like that to give me their opinions. (I lost my computer hard drive this week due to a virus - so I hope they get back to me - lost all my mail and addresses :>(
What I have found out however is that a MAJOR governing factor in the performance of a card is the driver, which is often overlooked. According to one guy "in the know", the best possible card is crap unless the driver is stable. I hope to find out more and post it.
Another very interesting thing. My partner pointed out one flaw in Frank's theory (writing to him about it). , which relates to daisychaining from one piece of gear into another via AES - clock and signal. The further down the chain, the bigger the problem, even if you use the best clock on the planet. Sending signals AES - needs very short cable DIRECT from the clock source. So, in other words, if you have 5 pieces of gear, connect each direct to the clock source. If the clock has insufficient outputs, you use a clock distribution box, one in - multiple out.
This is already done in video / post-production, where multiple rooms run from one central machine room, all requiring perfect synchornisation, normally all running from one single machine room located clock source.
Unfortunately it seems that "us in audio" still have a bit to learn.