Too many DAM Catalogs

I love Lightroom. I hope to love it more when version 3 comes out because I have a problem in my DAM management since moving over from Iview. I did not upgrade to EM2 because I was tired of flipping forth b/w two programs and iview no longer worked for me with my upgrade to Windows 7. (issue with Quicktime versions after 7.5. QT 7.5 not compatible with W7 and latest QT not compatible with Iview) So I moved everything into LR Catalogs and coverted my collections to keywords. Now I struggle. I have my catalogs divided into Weddings, Jobs, and Image Bank. Weddings works alright, because it is rare that I need to access it except for portfolio changes. Jobs if full of paid work that is not weddings and I have two catalogs One prior to 2005 and one 2006-today (90k images). Then I have Image Bank which is personal work but also includes potential stock. (40k images). In Iview with the 2gb catalog limit, I had divided it smaller and it worked ok because I could search across catalogs, have several open at once and create new catalog for certain projects that spanned several different archives. With LR this is not the case so I created catalogs that spanned larger time frames, but I find even with 8gb of ram (LR set for 2gb max) and quad core processing, those catalogs are clunky and slow. So DAM-wise I'm stuck. LR seems to constantly want to reproduce previews as you scroll through 100s of images.

Is the LR EM combo the answer to managing and searching large libraries of images?

What is a DAM strategy for using LR and having images that are cross-purposed in 2 different catalogs? (ie I have some shots in my "Jobs" Catalog that also need to be part of my "Image Bank" catalog)

Any thoughts appreciated.

Oliver.