Fiio, CMoy, PA2V2 - take your pick. These are pretty much your only choices in your set price range. I've tried them. A well designed and built CMoy will give you the most flexibility, especially with a dual gain (see BSG on eBay). PA2V2 good for low impedance cans or IEM. Fiio - well, you get what you pay for.
Now, if you want a long term amp, I suggest bumping the price range from $100-300. You're be in another world, one which you'll never want to leave. If you go this route, I highly suggest a worthy set of cans with the amp to do each other justice.