SMF-
Hallett is known for their great build quality and I would suspect (never been in one) that the cat is no different in that aspect. I personally don't think the cat is that big of a seller for them. You're right, they built their rep on Vhulls and I'm not sure their cat every caught on. It has the traditional lines of a hallet, definately an original tooling effort. I'm not a big fan of the deck/engine design on the back. But again, its a Hallett and you are going to get a good quality boat- ***boat and Powerboat are always praising their build quality, gelcoat, workmanship, etc. I love the hard wood floors with snap in carpet- super classy!
As for then engines, they will most likely put any engine in it you like. Merc HP 500, 575 SCi, Pfaff, Teague, GT Perf, you name it and pay for it, and I'm sure you've got it.