A version of DAZ studio will work with either Bryce 5 or 6. On the other hand animating materials got busted in Bryce 6 and hasn't been fixed yet. If you just have to have the ability to export your booleans or if you want all the extra materials then I'd go for Bryce 6. If you wan't to pose and change within your Bryce scene or even run animations I'd stay with 5.5.

Poser has never been integrated with Bryce though a fellow called conan sold something called easypose that worked way back in Bryce 5. The advantage of using poser is mainly the characters you get with the purchase.