I'm assuming you want something portable. If ultra-portability is a concern, you may want to look at the supermini by fixup. I've read good things about it.
If you can go a bit larger, but not much, you could contact one of the Head-Fiers, such as JMT, who builds amps.
Or you could check out the Airhead or Total Airhead from Headroom. There's a wide range of choices......it really depends on your budget and what you are looking to do with it.
I can tell you from experience that the Eggos sound great without an amp, and better with one. I'm quite happy using them without an amp.
As for how much better, I don't know if I would use the term "drastic improvement". Only your ears can decide how much of an improvement there is, and whether it was worth the cost.
Hope this helps.