Tom,

Doesn't look like the sub channel on your amp can be bridged. Looks like the listed rating is RMS vs. the Alpine which is max power. RMS is more meaningful when comparing amps. Max power to RMS gives you some indication of dynamic range.

If you wire your subs to present a 2 Ohm impedance (most speakers are 4 ohm) to the amp, then the amp will actually be putting out 500 watts from the single sub channel.

Given that you need tight low hitting bass, I'd go for a sealed box and position it in your trunk so that it is corner loaded. I'd also skip the 2 sub config and go for a single 15" sub with dual voice coils and wire for 2 Ohms. The 15 will hit lower and give you room to grow with a higher power handling limit. I like the JL 15W3 for best value. But, I'd drool over a 15W7.

If you got the RSX Type S, then you also probably have the Bose sound system. Do you want to sell the factory sub that came with your car?