That's a very good budget. Try and look for at least a 2001 vehicle, as this is the first year for the Performance Improved cylinder heads (an additional 20 horsepower), and if you can score a 2003 or newer, then all the better.
Personally I favor the early 2003 models produced in 2002, known as Job 1 vehicles. Starting with the second production batch in 2003, Ford did a lot of decontenting on these cars and they lost some elegant features that were standard on earlier models - black b-pillars, automatic parking brake release, underhood lighting, remote fuel door release and front seat pouches to name a few. So the Job 1 cars combine the quality of the old cars with the newer features of the current platform - hydrofoamed steel frame, rack and pinion steering, redesigned suspension, knock sensor giving you an additional 4 horsepower, etc. I just feel the new cars are more fleet orientated, which is part of the reason why I don't like them as much as the earlier models. Worth mentioning, however, they are superior mechanically compared to the older versions.
Also worth mentioning, a small percentage of the cars are equipped with a factory option known as the Handling and Performance Package (HPP). The package consists of a dual exhaust system, 3.27 gear ratio, better springs, slightly harder riding shock absorbers and an up-sized stabilizer bars. A different set of wheels are also part of the package. Pre-2003 HPP cars are very easy to identify, as they all have the lacy-spoke wheels:
The 2003 and newer cars do not sport different wheels on the HPP models, although the Grand Marquis used Crown Victoria LX wheels with darker inserts. These wheels are also found on Grand Marquis LSE models, which come standard with HPP and a floor shifter:
The Crown Victoria version of the LSE is the LX Sport, which also comes with a monochrome paint scheme and 17" wheels. Good luck!
