KING DRANZER
100+ Head-Fier
I find it's really hard to beat the price of the HD6XX and MCTH+DAC combo. The pairing gives you a nice full sound, it’s slightly punchy, does a great job giving instruments air, instrument placement, and it sounds great for most genres. If you won’t be using it on the go this is an incredible deal. You’ll have to sacrifice a bit of the bottom end because of the nature of the headphone.
If you want another great match the HD6XX + Schiit Jotunheim+DAC will give you speed and technicalities and fill out the bottom end (it gives the HD650 bass) but a very intimate sound stage. You’ll also lose depth compared to the MTCH.
The last recommendation I could give are used Massdrop TH-X00. They go for $200-250 on eBay and paired with the MCTH or Jot sound great. The Jot brings the bass hard but the treble may be hot to people. You can adjust the sound of the MCTH by buying a warmer tube which should ease the hot treble peak. The sound stage is intimate and instruments don't breathe like they do on the Senn.
The HD6XX and MCTH+DAC combo falls into your budget new.
The HD6XX and Jot or TH-X00 + Jot will have to be found used.
The TH-X00 will be needed to be found used but the MCTH+DAC can be purchased new.
The only headphone I found that sounded fantastic out of most sources that were easy to drive were the HEX-V2 but those now are $1000 (Sundara).
Yes I definitely agree that for that price HD6XX is definitely hard to beat it. But as I am ready to spend nearly 2-3times more I am bit dissatisfied by its performance specially after trying out some of the costlier headphones. I am trying to get the best I can get for my budget with least compromise possible. I have no idea how TH-X00 sound as Fostex is not available in my country at all. I have no intention of buying amp.