Trevor,
Looks like you're way ahead of me here. I've never used either miniDSP or hypex. I haven't researched the miniDSP. It just looked like an easy, ready made, solution for an active crossover ... nice to know about the noise floor issues.

Since Toole's book is the one on my side table I might as well finish it ... I'll have a look at David Howard's book ... although I think I'm already getting too deep as this is really a side topic for me ...