Based on the headphones I've listened to that are on Marco's list, I think his reviews are pretty spot-on, FWIW. I love my H6s. I recently picked up a pair of HifiMan 400i after testing a few pairs of open-back models, and I'm honestly not so sure that I like them better than the H6. They're different, and they're quite good, but if I could only have one pair, it might be the H6. Gotta find some time for A/B comparisons!
Anyway ... I've used the H6 a lot with the Fiio Q1 portable dac/amp, and I think it's a really nice pairing. Pretty neutral, black background, adds a little to the depth and soundstage. I don't have a ton of experience with amps, and none with any over $200, but I've been really happy using the H6 driven by Q1 (low gain, bass boost off) coming from either my MacBook or an Android tablet with an OTG adapter. Q1 can also function as an amp-only via 3.5mm in, but to my ears the sound is a little better with the DAC in play.
Q1 is going for around $70 online in the US, including from Amazon, whose return policy is quite liberal if you wind up not liking it (and don't have a moral issue with test driving on Amazon's dime).