Also make sure you get one that is undectable by VG-2. This is what the cops use as a radar detector detector. A detector that is undectable by VG-2 sends out less noise than others and will not set mine off! Nothing makes me more angry than sitting at a stop light next to someone who has a crappy a$$ detector that sets mine off all the time.
The better detector, the better sensitivity (range) and less falses (some have a false detection) you will get. Look at getting a Bel. They are pretty good and they are not too expensive. Last years Bel 980 is good and can be found on ebay cheap.
Help out fellow detector owners and get one that won't set other people's off PLEASE!!
Mish