You could do worse. I would personally use a different sub, and I hold the opinion that sealed boxes are better. They ARE more accurate, and less boomy. It sounds like that's what you're after. As I mentioned, I highly recommend Infinity products. I use them in my car, and I love 'em. I'm with ya though, on needing a sub. I plan on a single 10" when I can afford it.
With that setup, you'll have loud bass for sure...that's a 300w RMS amp!!! Personally, here's my recommendation for ya.
Amp: Kenwood KAC-5201 40x2, or 120x1 bridged (the way you'd run it) $99.99
Sub: Infinity Reference 1030w (Handles up to 250w RMS) $89.99
Box: Q-Logic QLH-CL10 (10" single hatch sealed box) $59.99
Also, remember that you'll have to get a wiring kit for the amp, and speaker wire for the amp to the sub. I've got you at $250 for this setup, plus wiring.