Hi Jay
I will do my best not to turn this into an advertising pitch for KBR..... 
Lots of our guests like to make the most of what North Sulawesi has to offer by spending some time diving Bunaken National Park on the west side of Sulawesi - and then switching to Weirdcritteristan in the Lembeh Straits.
Bunaken is classic diving: reefs, walls, great viz, turtles, the occasional shark. Lembeh Straits isn't. It's a freakshow. Viz of maybe 15-20m. If muck diving is your thing, I'd suggest 2-3 days diving in Bunaken (you may as well do it when you've travelled all this way) and then a week in Lembeh. Any of the major resorts will organise transfers for you. We all work together pretty well.
As for Lembeh resorts, modesty forbids me from overly promoting KBR - there are lots of good places to suit all budgets: NAD, Lembeh Resort, Lembeh Divers, Kasawari, Two Fish, Lembeh Hills - they're all good. (apologies, colleagues, if I havn't included everyone - no offence intended at all) And KBR of course - the first resort in Lembeh. Home of Fine Diving. Good nosh too 
The diving is just wicked!