Since the OP asked about what new car (or close to it) I would buy with $20-30K, I'll stick to that restriction and list a few:
1-2008 Mercury Grand Marquis LS w/tutone package, chrome wheels and all the accessories. Get a Lincoln for a Mercury price! List price is around $32K totally pimped out but dealers will let it go for less, say $30K without a fuss. Large, comfortable, safe and they still get 27 MPG on the road.
2-2008 Scion xB with everything in the catalog. They run around $25K totally loaded. 35 MPG with the convenience of a minivan and the economy of a small car.
3-2008 Dodge Charger with Hemi power. Not much room for options with the $30K limit but if I have to choose between a loaded V-6 and a stripper V-8, I'll take the V-8.
4-2008 Ford F-250 XL Supercab with a V-10. When set up the way I want it, it lists for $31,050 and a dealer will be happy to sell for $30K, so the limit is met here. If the limit was higher I'd go for the King Ranch!
5-2008 Ford Mustang GT Premium level with bling and accessories. It comes to $31,185 the way I'd order it and once again I do believe the dealer will be happy to let it go for $30K.
6-2008 VW New Beetle SE Convertible goes on the list as my combo of Euro and retro and ragtop! Loaded up gets me a Wolfsburg Blitzer for under $28K. That's nowhere near what a VW Beetle cost 40 years ago ($1800) but then we're a long ways away from those halcyon days!
7-2008 Dodge Caliber with all the goodies will run in the low $20K's. They even come with a Boston Acoustics sound system as an option!
If money is not limited, I get the 2008 Cadillac XLR V-Series with 443 HP. All the performance of a Vette with all the luxury of a Cadillac plus it's a 2-seater droptop hardtop! $102.5K puts you behind the wheel of a blastolene special and at least you'll look like you spent 6 figures on this puppy...LOL!
Rick