I'm realistically trying to source some cans that are easy to drive whilst I try and fund a decent $200-$400 Amp DAC. Which amp in your sig are you running?
Both.. the Arrow is my portable amp.. the Audinst functions as my desktop DAC/amp. At their respective price points, I'd say there's few, if any, comparable that beat them at what they do: clean, neutral, uncolored sound with robust power. Their sound characteristics provide a lot of versatility (to my ears) as they do a great job preserving the character of whatever phone that is running through them.
The 598, when run through the Arrow or Audinst amp, doesn't transform into some magical unicorn.. vs how it sounds amped.. In my experience, the amps improve dynamics, cleans the overall sound up so the microdetails are more easily appreciated, and the sound is simply more robust. In phones that have a midbass hump, the amps do an excellent job of rounding and tightening that area.. in phones that suffer from shrill or uncontrolled treble.. the amp smooths and sharpens the higher frequencies..
Those are the types of things I look for and appreciate in amps.. I'm not looking for a <$500 amp to turn my cans (most of which don't need an amp to sound great, but certainly take advantage of the cleaner signal and/or additional power) from Jekyl to Hyde.. I simply look for improvements around the edges of notes and for a more lifelike, detailed presentation.. the Arrow & MX-1 deliver that in spades.
The Arrow in particular is an amp that continually amazes me by just how robust & clean sounding it is.. it a got a gorgeous exterior and the craftmanship put into to it under it's sleek appearance is just as impressive.. at the time, it seemed like an incredible amount of money to drop on a
portable amp.. instead of toiling with the plethora of portable amps in the crowded mid-fi market, I'd just suck it up and throw down for what is considered in many circles here as a gold standard among portable amps.. After 6 months of ownership.. I couldn't be more satisfied with my decision.. I'm so satisfied, I haven't even visited the Amp forum in search of upgraditis.. which I suffer none of since receiving the Arrow. Same goes for the MX-1.. it's been a workhorse at the desktop.. sounding great with every can I've thrown at them.. and I haven't gone in search of an upgrade since buying.. and don't plan on it, either. It is portable too so if you've got a laptop, it quite compact and unnoticeable if dropped into your bag/backpack.
With the Arrow & MX-1, I've no longer had to go in search of bigger and better.. I've taken the money I might have wasted in that venture and instead dropped it into my first set of customs (1964-Q)..
I don't have $600 or $700+ dollar phones.. 90% of my listening is done with my iPhone.. I didn't see the reasoning in dropping an exorbitant amount of money on an amp or DAC that will be powering mid-fi priced phones (some of which can compete well with hi-fi phones).
It's all about keeping your gear and expectations in perspective. Sorry to get off topic or soapbox-y.. hope my experience and reasoning helps.