1- I do not think anyone here can give you a "MAX" for all credit unions, as each one sets its own policy and lending standards. You are the member of PSECU, call them.
2- Consumer Reports rates the S550 as one of the worst values you can buy.
3- Most average banks and credit unions do NOT finance $100,000 NEW cars. They do not want to deal with the depreciation and being stuck with it in the event of default. The dealer will have the financing institutions in place for you to use.
4- Without a specific on "Lot of cash down" there is no other real guidance. On a 100K car your tax title and fees will fall between $10K-$15K, PSECU charges an interest rate penalty if the amount financed is at 100%-130% of MSRP
Assuming you were looking at a valueof less then say $60,000 to finance I do not see you as having a problem assuming all your other factors line up.
