I agree with AnotherDude.. Sonicelectronix has the best prices, Crutchfield has the support after the sale and the install diagrams, kits, wiring harnesses. For a newbie Crutchfield is the way to go. That way if the newbie runs into trouble a call on the phone and it's solved. Crutchfield will stay on the phone with you til it's fixed! no joke! back in the day I had issues with a new headunit, they would troubleshoot til it got fixed. It was actually a metal shield in the dash acting as an antenna for the alternator! They had this mu-foil they sent me to wrap that and instant fix.
Ok anyway, for the original question. there are many many options out there.
There are single din and double din sizes. The double din is like our stock headunit size. have to figure that out first, then other features like usb? ipod? bluetooth?
If you want a nice headunit JVC makes a nice double din size in that price range, there are two.. one is 200 and the other 250
JVC and Kenwood are now sharing production of their products. I think it was about a year or two ago that they merged into a production alliance. So Kenwood and JVC are the same now. which i think is a good thing, Kenwood has always sounded great and JVC has offered features others haven't. Put them together, good merger!