Outlook 2007 / Vista / Windows XP best combo needed

Hi all

Sorry for the cross posting here in advance..

I 've run Windows XP & Outlook 2007 & BCM 2007 on a good computer and
found that it ran horribly opposite a 32 bit Small business Server
2003. I have an email inbox data file that has been very very big
( which I have since shrunk to 700 megabytes.) I get a lot of email
every day.

I've also seen a copy of Vista 64bit Outlook 2007 & BCM run flawlessly
with a 2.2 gig mailbox file

Here's my question, if I upgrade to Vista 64 bit with Outlook & BCM
can I run that against a 32 bit SBS server for both the Outlook /
Exchange elements and also can I have SQL express in 32 bit work with
the 64bit version of the software I am running on the client
workstations?

What is the best solution (without going crazy) I'd really like to run
Outlook 2007 & BCM with the data file on the SBS server..

Thanks for everyone's input.