I've only ever used an iBasso D4 Mamba, just because it fits the bill for what I need it for, isn't too big, and is good product quality/features for the price (most others in this feature range are $250+).
http://www.ibasso.com/en/products/show.asp?ID=44
There are some that are cheaper and some that are more expensive/feature laden; you can try looking at head-fi.org for individual product reviews, but ultimately the best thing to do if possible is find someplace you can try them out. Take YOUR cans and see how they sound on the different amps available; every ear is a little different so results can vary wildly from person to person.
Edit: Trying them out goes for headphones too, if you can help it. Nobody can tell you exactly how your ears and brain process sound, so what might sound amazing to one person may be off-putting to another. The issue is almost as diverse as music itself.
When I was poor my daily headphones were the Senn PX100 coupled with an ebay CMOY. Might want to look into a CMOY amp if you're on a budget or make one yourself.
Yeah, CMOY is great if you just need a basic amp for your ipod or something and aren't audiophilic enough to be picky about the finer points of the result or need extra features; it'll still be a marked improvement over no amp at all. Super great budget option and has the benefit of being a fun DIY project.