Just keep watching. You might also see about National's Emerald Club, where you reserve and pay for an Intermediate but can take just about anything (including convertibles and vans) they have except Luxury calss.
Also be aware of what is in a quote. In Florida there is a $2.05 per day "road impact fee" as well as about a 10% Airport Concession fee and some other fees. Everything, including all the insurance and nuisance fees, is subject to Sales Tax