I'm looking to upgrade my headphones and currently leaning toward a HiFiMan HE-500/JDS Labs Objective2 combination (or possibly Sennheiser HD650). Any opinions on this combo? My source would be an iPod Classic (5th gen) or possibly a PC or tablet. I see that when ordering an Objective2, you have your choice of 2.5x & 6.5x, 1.0x & 3.5x or 1.0x & 2.5x. Which would be the best choice? I don't currently have a DAC, but will probably get one eventually. EDIT: Sorry, realized I should have posted this in the help/recommendations thread.