The GM classic card is still a great deal. Especially if you're leasing, since the accumulated credit comes off the top. So for example, if the total payments for your 3-yr lease will be $10,000, and you pay it in full up front, you might get $1500 off. Make your best deal, then use your GM card points to knock another $1500 (or whatever) off.

I've done this with two different leases already, and next year will do it yet again