Nice work - very quick and the presentation is very clear.
I think though it's more useful to USA based people where the insurance situation is different. Here in the UK comparison sites that quote prices including all applicable taxes, fees and insurance (LDW, SLI & UIMP) are more usual and more useful to us. Have a look at one of the sites that uses the
CarTrawler software like
Argus. I know CarTrawler doesn't apply coupon like yours and that's a big plus for you but it does illustrate the insurance thing I mean.