Recomend a sound card for bass shakers

I currently use the on board sound for bass shakers it's a Realteck, I'm using 2 Fosi v3 amps supplying 2 buttkicker Advance on 1 amp and 2 buttkicker lfe on the other, the amps do power them but only if they are near 100%, I'm thinking that if I got a sound card with more or variable gain that it might sort this, not sure it would but in my head the theory works.

So I'm after a recommendation of a sound card with 4 channels and high or variable gain.