i have just purchased a pair of 535's to use with my 160gb iPod classic. 1 week of running in and have to say I am very impressed. Does anyone have any suggestions for a decent portable headphone amp to further enhance my listening experience? I have previously used the FiiO e11 with iPod and B&W P5's but found it too bright sounding. I have sold the e11 so cannot test it with the 535's. Would purchase again if advised that it could provide the warm, laid back sound I prefer. Any other suggestions? Looking to spend no more than £100 / $150.