RIGHT ON!! I would just keep it. If you truly need a MBP just sell it. Since you got a 1 year warranty on it did you know that Apple will refund you for the remainder of your Applecare warranty on your 2009 iMac? Trust me, they will (I've been through 3 upgraded replacements) but you had to at least discussed that with them. It may not be much since it expires in March but you may have $10-$20 coming to you. If you didn't discuss that with them call them and they will look it up.
If they don't talk to you about the warranty then they generally carry over the old warranty to the new Mac and you won't have an opportunity to extend the Applecare after March so make sure with them before you get started on your new iMac.