Yes, you can drop the W3570 in a base '09 Quad.
Those models use the IHS (integrated heat sink) on the processors, so you won't have to worry about finding the thermal gap material needed with the "naked" processors used in the DP systems.
You do have to be cautious though, as you can bend pins on the socket. The DP systems don't have the latch you find on PC boards (LGA1366 or any other for that matter), and IIRC, it's the same on the SP models as well.
As per the 2006 MP, the fastest chip you can drop in, is the
X5365 (3.0GHz Quad Core units). Several people have done it, and located deals on eBay for the CPU's (they pop up from time to time).