Sennheiser HD 650, can be found on amazon, they have a wider soundstage and more bass, but slightly less amazing, but still pretty good mid/high end than the highly praised HD 600. As for an amp, the Darkvoice 336SE that's here on massdrop for a great price, just fyi it can get rather hot. Out of the box it is an excellent amp, it will elevate the highs, and may open up the soundstage a bit while boosting bass, but you can later on buy other standalone tubes to put into it and you can influence the sound signature to your will, you'd just have to find out which tubes do what. The Darkvoice however does not come with a built in DAC, so you would just have to buy a cheap standalone DAC to fit your budget. OR hold off on a DAC (because while yes a DAC helps a lot in sound, it is never fully needed like an amp is) save up some money and get a good DAC.
Other recommendation is the HE-400i, with any sub $200 amp/dac combo, that headphone is planar magnetic and purrs like all planars do, but it is a bit pricey and will force you to get a cheaper amp/dac.
I know this is a lot, but I hope this helps.