Upgrading to 2-10's would definitly make a noticeable difference/boost in your low end sound range. You lost me on the cross-over part and caps, if your asking if you'd need a capacitor to run subs, you'd only need one if you bought an amp, and even with just one amp, a cap is not nesecary. I hope that helps, but i can assure you that 2-10's would be very noticeable, but i can't stress enough to go with a good quality sub, if you get something cheap, it will sound cheap.