Well you can investigate the different models in the Wiki on this site. When you are talking about digital models you can save a little by going with older models, you're probably looking at a difference of $200 - 300 between an older model like a 785D (with card), 796D etc... and a brand new digital in the box... Or a newer "used" model. You can get a used 996t for about $500. The 996xt is $495 US plus tax and shipping. I got mine for $650 CDN from another member on this site. The newer models can be controlled by computer (with programming) and this makes it much easier to program your unit.
I have said on several occasions on this site that I like both the 996xt (Uniden's latest digital model) and the PSR-600 (Grecom) but for different reasons. I like the 996xt for trunked P25 (digital) and I like the 600 for conventional (one channel, non trunking) P25.
So again you have to figure out what you want to listen to, what radio systems are in your region and then go from there. Keep an eye on the classifieds here on the site.