Odd Question: Portable Amp for HD600 for $200-400 better than the cheap, but not so portable, E9

Hey all!

I know this is a little odd. Right now, I have two E9's. I use one for the home as a semi-portable, right now with HD598 and SR225i. And I have one for the office with the HD600. (I haven't really heard any better desk top amp, but love that combo.) Is there a portable amp that I might be able to replace both E9's, not lose anything in sound quality and...here's the kicker, and the part I'm skeptical about, still powerfully drive the HD600. So asking if their is a portable amp that is can do better with the HD600 than the E9 can...

Thanks!