That's a pretty open ended question that needs a little clarification. For example, what size tank? hang-on or in the sump? If in the sump, do you have room for a skimmer with a pump? As one mans good price is another mans forture what price range? what kind of bio-load? FOWLR? Reef?
There are alot of different brands and styles that could work but it would depend upon your needs and environment.