Note that rental companies are NOTORIOUS for not being completely upfront with their pricing. Most will not list the airport concession fee (often ~10%), none will list with tax (another 6-7%+), most will require some sort of token liability coverage (even if you have coverage through other means), and every once in awhile you're required to pay a deposit (uhhh). Figure on adding 25% to the bill through various pieces of insanity like that.
As far as road trip cars go, I just got out of a V6 Challenger. Big, comfortableish, and quick enough to get into trouble (but not quick enough to do donuts without rain)
I quite liked the challenger when I had one as well.
I've been using carrentals.com which seems to do a decent job with pricing.