Custom Subwoofer Ideas... Which one?

[Tahoe Gator]

The number of rooms I need a subwoofer in now outnumber the numbers of subwoofers I have. Here are some ideas I am entertaining:

Option 1: Buy another one. Pros: easy. Cons: cost.

Option 2: I have an NAD 2600A amplifier (150W RMS, much higher peak, and much much higher if I bridge to mono) that is not being used. I've been thinking I could go buy a high quality car audio subwoofer driver (or two?), build the appropriate box to match the driver(s), and drive it with the 2600A connected to the subwoofer out of my A/V receiver. Pros: cheaper. Cons: Ties up the amp in case I need it later. My time in labor.

Option 3: I have some pretty high quaility car audio amps lying around, including a 200W Soundstream that can be bridged to mono. A while back I was in a electronics surplus store and picked up a super beefy 12V DC power supply. The thing weighs more than some home audio amps and I believe it can deliver plenty of amps. I could build the same box mentioned above, but instead power it with the power supply / car amp combo. Pros: cheaper. Uses stuff collecting dust otherwise. Cons: ?

I am a reasonably accomplished carpenter and an electrical engineer, so the construction is relatively easy. The real question is sound quality: would the NAD amp / car audio woofer combo be much better than a mid-range suwoofer (such as Klipsch KSW12)? It would seem the amplification quality of the NAD would be beyond comparison to a $400 subwoofer. I would think even the car amp on a massive power supply would be also. But, I am obviously posting for some thoughts. Thanks for any suggestions.

[N. Abstentia]

I definitely wouldn't try using a car sub in the house..keep in mind a car sub is designed to maximize output in the tiny space of a car, and most of them are designed for that one note thud which is poor for home audio.

You might try posting in the DIY section for some ideas on which raw drivers you could get for a good home sub.