Recomendations for a good stick pack?

[dadgummit]

I am working on making my Cen ME16 faster and I am now down to the battery. It only fits 6-cell sub-c stick packs and I am looking for as much amperage and runtime as possible (within reason).

I see that Cheapbatterypacks.com has Elite 4700 MAH calls upgraded to being soldered diectly together (as opposed to those thin tabs they use) for under $50 each. Has anyone had any experiece with these?