Panasonic CQ-C1120U is in your price range. It is not the best but it is sort of what you are looking for. You can buy it anywhere from $70-100. Depends on where you are looking. You can also go on Ebay and look at car stereo and check out the buy it now prices. You just have to take the time to compare and contrast on crutchfield.com once you get it down to the head units you want.
go with kenwood, jvc, or pioneer. used is tricky, it might be good, it might die tomorrow. i would avoid it at this point. I assume that you dont have money for speakers or amp so you will want some kind of eq settings, pioneer's ezeq allows the most adjustments. most stereo equipment goes on sale in the spring as new models are introduced, so there will be some decent sales soon.