People have had different experiences I guess. For example, head-fi user wind has had positive experience with the PRO550's (assumingly same as dj1 pro) and said they had very fuffilling bass; whereas when i listened to them, the bass was very weak. Hes was running unamped out of a cowon, i was running unamped out of an onboard card/iphone.In regards to the shures, whats keeping me away from those is both the comfort, and build quality(and coiled cord, not my preference x]). From what Ive been reading about the build, it seems as if the product shouldve been branded as "hasbro".
Those are the reason for your different experiences, onboard sound or iphone as a source will never deliver truly fulfilling bass especially for a Pro550. Cowon especially are known for having amazing bass boost capabilities which is worlds apart what can be said about onboard sound or iphone. You're missing out on a lot as long as those stays as your sources you use.