http://www.amazon.com/FiiO-E7-Portable-Headphone-Amplifier/dp/B003E6K1VK/ref=cm_cr_pr_product_top

It's like I have new headphones. The bass on the Senn 448s is finally on par with the highs.

Gotta have this with it
http://www.amazon.com/FiiO-L3-Line-Cable-iPhone/dp/B003UCESP8/ref=pd_bxgy_e_img_b