Subwoofer Quandary

Hello forum members. I'm in search of a good subwoofer driver for a potential DIY project.

For the last 4 years I've been using an NHT SW3 12" passive subwoofer at times with an NAD 214 amp bridged and more recently with the companion NHT SA-3 amp. This has been used for both my music system and home theater. Up 'til now the results have been satisfactory, but I am now in search of something better.

I'm in the process of buying a Bryston 7B to use as the new amp to drive whichever driver I choose, but I've also entertained the possibility of getting the active Revel B15 or REL Stadium instead. I thought of getting the passive Revel Sub 15 to use with the Bryston and a Paradigm X30 crossover I have lying around, but Revel tells me I won't get the most out of the sub without using their $7000 LE-1 crossover/amp. I'm wondering if this is all marketing or if there is some substance to the claim. I was told that the Sub 15 besides the amp and crossover needs equalization which the LE-1 provides, and that authorized Revel dealers have equipment to fill these needs. What equipment I don't know.

I'm open to the idea of a DIY, especially if I can find a driver better than the NHT 1259 for the project. But should I be looking into the Revel and REL options more carefully?

Thanks for your opinions.