They essentially made me give up everything else. I sold off my higher end gear, and stuck with just this and the E17. That's how strongly I feel about the MA900.
They aren't mid-fi beaters (K70x, DT880, HD650, HE-400 are all generally better, with some caveats). They're just really solid at their price level, with an agreeable, all-purpose sound signature (akin to something Sennheiser would put out), with a large soundstage, amazing imaging, and non-fatiguing sound. Be realistic about them (put them basically on a HD598 refinement level, just a tad better, but not 650 level).
What may sway you towards them is how they feel. It's hard to go back to general headphones after wearing the MA900 for a period. That, the price, and them not being finicky as to what amps you pair them up with make them an easy secondary choice, when you're fatigued from wearing a standard headphone.