If you are indifferent to advice why are you asking questions?

The sound card is bad. It is consumer level and is not made for professional quality recording.

Here are the comments of one professional sound engineer I know on the Creative labs cards.

That asides you still don't have enough inputs band how are you going to interface with the XLR backs of the SM57s / SM58s ?
There are no XLR inputs on the cards ! Even i there were you could only use 2 (stereo L and R- Id forget about the RCA inputs) at one given time.

One solution may be to record to a desk and mix there in which there is no point in having posh mixing software.

AS far as software goes if you are willing to drop 600 bucks o it Id go for Sonar 3. However to take full advantage of this you will need to have the appropriate hardware, like enough Mic's.

You may also find that latency becomes a huge issue with this card if you are recording at a high bit rate / sampling frequency. I saw the specs in the Creative website and in order to get the latency down (at192/24) they had to drop a channel and record in mono. This is the opposite of what you want.

My advice is buy a Tascam portastudio with 4 SM57 / 58s.

You can then import the tracks from the portastudio into the computer later and mix, edit etc at a later date. You can also then export the tracks as MP3s etc

OR you will need a digital interface like the TASCAM