Hi, I'm looking for a pair of cans to replace my Sennheiser 558s.   The 558's have great soundstage and clarity but I find that the bass is lacking and it seems to be a very neutral headphone.   I'll be using my headphones with my iPhone 6 extensively.    I've been looking at the...

I have never owned any headphones that costed over $20 so I went out on a limb buying the sennheiser 558's for about $110 (refurbished)   Questions:   1) Will I need a portable amp to get quality sound from this headphone? This pair of headphone comes with a 6.5mm to 3.5mm adapter so I can...