Looking for headphone amp/DAC

Never heard the Z Dac but have owned an iFi Stereo 50  & can attest to them making a highly musical DAC with a super low noise floor that can really dig detail out without being harsh.For $150.00 I doubt you will find many that compete & certainly none that better it..

Thanks for your response. All the reviews are good

I prefer my Audioquest DragonFly Black (with Jitterbug) before my iFi nano. If you can go up in price the DragonFly Red is probably even better.

I use the Dragonfly Red and am very happy with it.  I tried the Jitterbug with it and transparency and soundstage were both negatively affected so i just use the Red on its own.  FWIW. 

I’ve got those Sony MDR 7506, I think they might be the brightest sounding headphones that ever were.   Brighter than my Grados even.  You are going to need to carefully select the amp for those phones. I’d suggest something that has a warm sound signature.  
 And just so you can get a different flavor, I suggest getting a pair of Koss Porta Pro headphones.  A warm sound but still good detail.  Don’t be thrown by the looks, they’ve been in production since 1984 for a reason.  At 30 bucks or so, you’ll thank me.