Mountain Biking - Mountain bike for dirt roads

I live in a rural county, (outside of Athens, GA) and most of the roads near my house are highways where people drive fairly fast.

I had planned to buy a road bike and find some deserted roads and ride there. Then today I discovered there are probably 100 miles of dirt roads throughout the county that I can get to without riding on the highways.

So, now I'm thinking mountain bike. I've been riding my wife's mountain bike but it's a little too small for me.

I'm looking for a bike that will hold up on dirt roads, but I'm not really planning to do anything too crazy on it. I'm just going to ride on the dirt roads. The area is pretty hilly, too.

Can anyone suggest a good bike for that?

I was planning to get a Bianchi road bike, and have established a good relationship with the LBS that sells Bianchis. Are their mtn bikes decent?

I'd like to pay under $500.00.

Thanks for any suggestions.

A friend of mine has a Bianchi Grizzly and it seems to be a pretty nice bike. However, have you considered a cyclocross bike? Unfortunately, most of the cyclocross bikes I know of are over the $500 mark. The Bianchi Volpe or possibly a Castro Valley (if you're more inclined towards the utility/commuting features) looks to be very nice bikes for what you want.

Have a look at the Raleigh M-80 or (same bike, different paint) Diamond back Topanga.

No bike in this range is perfect, but in these bikes you get decent shifters and disc brakes. Or hunt the pawn shops for something used. Whatever you do, don't consider any kind of rear suspension at this price range.

For the $$, I have no regrets in purchasing my M-80.

Nomo