It is almost always a better deal for a DVC owner to rent points out and use cash to secure the vacation lodging they desire. It is also a little more work, but as they say, there's no free lunch.
Depends on exactly where and when you want to go though. The better Key West resorts may well go for more than $2,500 for a 2BR during peak season. Then again, the better Key West resorts might not be deposited to RCI, for the same reason that you are considering not depositing your DVC points. And, you may decide that throwing a little extra money in with your rental proceeds to get exactly what you want to be a fair price to pay.
Do a little bit of research on the various rental sites (TUG, RedWeek, etc.) to get a sense.