Thanks for the suggestions everyone! I ended up going through National. After many gyrations with different combinations of codes/coupons, etc. (found through Mousesavers and rentalcodes.com - thanks, Eeyore1954!), I was able to reserve an Intermediate for $130.xx for 5 days. That includes all taxes and fees. Because I'm an Emerald Aisle member, I'll be able to snag a bigger car at no extra cost (if there's one left on the lot).
Thanks again!
Sammy