I had read stuff about 10"'s sounding tighter,

That was probably Doug talking. He could be right, I've never installed 12's in any of my cars. I'm guessing that if you do things right, you can get great sound out of either 12's or 10's. You just have to be careful to get your box volume right and to provide them with enough power.

Do you know if those subs were designed to go in a sealed enclosure or a ported enclosure, or either?

And I'd also heard that bass is the first thing to leave out the open top of the car at speed and that it's a good idea to compensate.... but am I compensating too much?

As long as you can adjust the gain on the sub's amplifier, there's nothing wrong with going "big". Having extra power in reserve is a good thing.

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Tony Fabris