I suppose you can start calling a soundcard "professional" it is operates at +4 with balanced inputs.
From there, you would need to consider the s/n ratio specs, and possibly how well it deals with jitter.
Also, for a soundcard to be truely pro, it would need to pass a null test. Go to
www.digido.com to learn what that is all about.
The Lynx card has work clock I/O, two midi I/O ports, AES/EBU and S/PDIF digital I/O, as well as +4 or -10 operating levels on XLR connectors. It is full duplex (most cards are now a days), and has extremely low latency, especially low latancy for midi too.
It has NT drivers, and they have Beto ASIO drivers for Windows 9x systems. The NT4 driver has worked just as well on Windows 2000 as it did on NT4, but, I cannot use Wavelab with this card on 2000 because of a little mix up in Wavelab working with soundcards with integrated mixers with Win2K.
All that sounds pretty pro to me...
I think cards like the Turtle Beach, and possibly the SB Live would be considered "pro-sumer", and only because they do offer some digital I/O.
The consumer cards would be like the older SB and Yamaha cards.
Now, with the "professional" cards, you definately start getting into the whole subtle area of converter "quality". Some have converters that sound exceptional, some have more average sounding converters.
ProTools is a turnkey type system. It is made to utilize their hardware/software combo. The is also Soundscape, and Sadie too that are the same. I have seen a few other of these types of systems. The take that I get on the converter "quality" of these systems is that they are more or less in line with like the Echo cards. What makes these systems popular with major studios is that they come complete and just about ready to go. The hardware/software capatibility issues have been worked out. Also, ProTools and Soundscape, and Sadie usually do their own DSP. The computer that you run these systems on usually just "host" the software. When you go to execute some kind of processing, the external box usually provides the DSP. In the case of the Soundscape and Sadie systems, they have their own hard drives too. So really, the computer just is a way to get the GUI, and to execute DSP. Usually these systems have superior designed software.
Ed