If you're running Dynamics 6 on SQL7 - and you want to add CRM to that same box, I would be careful. Depending on what you want to add, and what you have (hardwarewise) it could drain out your resources, etc.
The GPS-Seibel product, for instance, is a huge resource hog. You really want to carefully consider whatever goes onto your SQL box - especially those which suck lots of resources (mail, CRM, etc.).
We have our eEnterprise 5.50 installation on an HP LH4 with 1.2 gb of RAM, two SCSI controllers (4 channels) and fifteen 10k drives configured into 5 logicals. I fight tooth and nail to keep other apps off that box..
Good luck -
//sse
Sean Engle
Admin/DirIS
ssengle@bswusa.com