[Klisk]

I absolutely adore my AT AD700's, even without an amp. They're pretty amazing.

I must say, though, an added boost of bass (be it with a cheap amp like the FiiO or even the EQ on your audio device) really brings them to their full potential. Stock they're generally very balanced but can feel a bit light on bass compared to other headphones in the price range. It depends on what you're expecting/are used to.

They're not demanding headphones at all, though, and the sound is just flat out great. Entirely usable without an amp.

 

[Acix]

Try the GMP 8.35. or the 435 S. Both share the same great drivers, @ 35 ohms.

 

[Moocher]

I've had the Senn 580s and the AT AD900s. I listen almost entirely to blues. Neither of those headphones worked for blues. The Grado 225, or even a lower model, will knock your socks off - without an amp. Grados are wonderful for blues!

Mooch