I personally finance my cars because I run a PTY/LTD business and it is the best type of expense to claim so for me my cash is better utilised elsewhere, i.e. in offset accounts, DIY Super or shares (although not right now).
But I suffered the same problems with obtaining finance as these cars are classified as "grey" imports... I have an outstanding credit rating with GE Money as I've had 3 cars through them with perfect repayments and the best they could do and mind you because of my excellent credit rating was 30% deposit upfront with 17% interest.. This I thought was ridiculous and after scrounging the internet for other finance companies, out of interest I phoned St George (I don't work for them) and they did it for me with no quams at 10% over 5 years with balloon or no balloon.
Interestingly they use the Redbook website for their evaluation reports, why don't you check out the value of your car there...
Good Luck!