A few recommendations on headphones;
-the HiFi Man HE-400i is a nice headphone, easy to drive
-the Verum 1's are another stellar headphone for the price, check out other "dealers" as some may have these in stock
-you cannot beat the performance either the Meze 99 Neo or the Meze Classic 99 headphones give you, great bass, midrange and top end
-some of the Audioquest headphones are also very nice, discontinued now but can be found used, Nighthawk
I am using many of the 'phones with a Rogue Audio RH-5 headphone preamp/amp, 2 tubes drives everything.