I have a CMoy from juice2214. I think it makes a nice pair with the TBSE1s; the soundstage widens and the vocals are brought back a bit. If you read up on Op-Amps, I think you'll find the OP2227 to be best suited to headphones like the Pro DJ100/DJ200/TBSE1s.
I was advised to buy a CMoy because apparently the E5 didn't have enough power. No idea about the E6, though.
Thanks for the reply. Now I don't know if I should sell my fiio and buy the cmoy. The E6 sounds really good with the TBSE1 but I'm not sure if the cmoy will be a big improvement over the E6 =/