...
hmm what do you mean by playback with the mixer? do you mean you want the soundcard to send out a signal to your mixer so that your mixer can then send a signal to the speakers you may have? if so, just run a cable from the line out of your sound blaster to your mixer's input. I don't know if sound blaster has 1/4 inch outs or 1/8 minijacks so you may have to buy a converter, but no worries they are cheap. To hook the mixer up to your sound card for recording, run a cable from your mixer's out to the input on your sound card, again you may need a 1/4 to 1/8 converter, i am not sure.
As far as pro tools, i'm sure it is equally as good, if not better, than any of the other recording software packages out there. There is a poll in the computer and sound card forum and you may want o check out that lists what everybody is using as far as sound recording software. I think cool edit pro was in the lead, but this really means nothing. I think cool edit just may be one of the cheapest available as well as n track and whatnot. they all have similar features but have different layouts and diffrent ways of getting shit done. just pick one and learn to use it good. A buddy of mine has like sonar, cool edit, cubase and pro tools. I personally don't see the point in having all of that as you would have to learn to use each one...? wierd...
anywyas, my rant is complete.