if you're looking for a cheap sub-$100 portable amp+DAC, I think Fiio is your only option.
E17 is $140ish, so over your budget. I would recommend the E70K at $90. Any sound quality differences shouldn't be too noticeable as they both use the same DAC. the E17 has more connections and a slightly more powerful amp, but the E70K is lighter and has a longer battery life.
Are you just planning on using it only for your laptop? Then you can consider options like the Audioquest Dragonfly 1.0 ($99 - older version; newer version is 1.2 for $150). If you are planning on using it for your android/iphone smartphone, you have to check if the DAC will work w/ the OS. You need to be able to do digital USB audio out. Usually, it's a matter of finding a DAC that is compatible with your smartphone operating system. for android, check out this thread for which phones work w/ which DACs: http://www.head-fi.org/t/595071/android-phones-and-usb-dacs
Edited by money4me247 - 12/16/13 at 9:33pm