If you are converting in earnest, pick up the Marriott Visa. It automatically credits 15 nights to your account, which translates into instant Silver and a nice jumpstart on Gold (you'll need 35 more actual room-nights).

Cost is $65 per year, but that includes a free night certificate (good for Cat 4 the first year, Cat 5 after that). And there's usually some sign-up bonus points too. Finally, the card earns 5 pts/$ on Marriott charges, so you'll want to use the card on your hotel stays even if you don't use it anywhere else.

The Marriott Visa is a substantial upgrade over the credit card they had in place two years ago - it's well worth it for anyone who can even use 1 free night each year, and it gets even better for someone in that 35-40 or 60-65 night range who would otherwise fall short of the next elite level.