I really can't help you a lot, as the specs on that sound card are minimal. It says it has speaker outs, but I suspect they are line outs. I don't know. No output impedance or voltage is specified.
In general if you use the DAC on sound card you get into no end of trouble.
If you are going to forgo a receiver, I would get a preamp with XLR outs and a good DAC and use the optical out from the sound blaster. I would get an electronic crossover and connect one Crown to the main speakers and the other to the sub. You gave no details of the sub, but I assumed it is an unpowered passive sub.
You really need to do better on these forums. You did not give a full equipment list. You gave no details of your speaker system
It is also polite to give hyper links to the equipment you list so we do not have to do a search. None of us know the details of every item of equipment made.
If you are going to ask for help, then you need to do a lot better. It seems to me you are not cut out to own any type of sophisticated audio gear and especially not high powered pro amps, which it seems to me you are likely to cause havoc with.