It all depends on a lot of factors.
17" MBP are getting harder and harder to find, especially those with some applecare left on them. I was in the market myself for the last few months and decided to go for a Refurb'd Sandy bridge (early 2011 with i7 Quad). I paid extra because I needed my laptop to be able to render/process HD Home videos and a LOT of photo editing.
Although I am sure the late 2010 with i5 MAY have been good enough, I paid extra to play it safe and to be able to have 16 GB of RAM.
IF you need the laptop for usual laptop use, email/surf/school work etc the 2010 model for $750-$800 WITH Applecare IS a steal.
You have to decide what your needs are and if the hardware you are buying will support that for at least 2-3 years.
IF you decided on a refurb'd Sandy bridge, you will have to spend at least $1899+tax + $300 for applecare