The Giant Sport series of mountain Bikes has a frame design that gives you increased standover. Haro has a frame design with the same advantage. Jamis makes the trail series with increased standover. The Trek Hard tails seem to have plenty of standover. I am only 5'9" and my Mountain bike is easy to stand over.
I also like the Giant FCR series bikes in that price range. The FCR 3 should work for you and if you get the right frame size, at 5'9" a 54 frame works fine for me.