You deff. want an auto. since you havent rode a lot in the past.
look in you local newspapers and autotraders to find something to your liking.
Polaris,Yamaha, and Honda all make great Utilities in the range of 400cc-500cc.
Suzuki i sort of the botttom of the utilitiy world. but if you take care of it.it will last.
polaris has a problem with weight. they are heavier than most, but that doesnt take away from the get up and go, most reviewers say. Can-Am/Bombardier is the top of the power class. but they are hella expensive. Hondas are mega Reliable, but lack a bit in the power end. Yamaha seems to have a great blend of power and reliability. Kawisakis Brute Force, seems to maybe be a bit out of your range power wise [very powerful machines] but if you think you can handle it go for it. and just a fair warning. if its not Kawisaki,Suzuki,Polaris,Honda,Can-Am/Bombardier,Yamaha. I would STAY AWAY.
cheap chinese quads are both lacking in power and reliability.
My top machines for this class i would recommend.
Polaris - Sportsman 450-500
Yamaha- Grizzly 450
Kawisaki - BF 650 [if you want the EXTRA power]
Honda- Foreman
this is like my longest post lol hope it helps