i know infiniti extended their warranty on the coupe (6year/70), my question is:
This is the 6th year of my car, do i still have warranty? Does it finish in 2010 or do they go by another date like the production date?

Really? I haven't heard that before. So a 2005 coupe with 43,000 miles will still be under warranty?

I have a 2004.5 Sedan. My warranty expired in March so I went extended.

You need to check your ISD (in service date). If you're still within the guidelines of the warranty, then you're still covered. FWIW I believe the 6yr/70k was for powertrain unless you have an extended warranty.

Is there a way to find the inservice date? Would car fax have that?

it would be on a carfax. BTW, if you have a receipt from any previous warranty work, the in-service date should be a field towards the top of the first page. Hope that helps.

who did you go with?

I went with Circle Infiniti in NJ because they had the best rate at the time, but from what I understand there is another dealership in AZ offering a better price. There is another current thread about extended warranties. The OP can give you the contact info of said dealership.