To be perfectly honest, I've only had these phones for a month, but I've been experimenting with them a lot, and I've found that they're actually not that hard to drive with an inexpensive headphone amp, or receiver.
However, and this is a big, and very important point, the source is extremely important. These phones are designed to reveal flaws in bad recordings and sound great with great recordings, and so the biggest change I've found is going from a mediocre source to a really good one, and also again, going from either low bit-rate, or just poorly recorded CDs to newer, better recorded ones.
Loudness wars in pop music also create problems for these headphones, and there is very little that the amp can do to help this. On the other hand, many CDs recorded in the 1980s are almost too thin sounding with these phones, and you really notice the recessed mids and sibilant highs in such recordings.
Ideally, of course, an amp will have a very low noise floor, low distortion, and good tone and speed, but I've found that even my Schiit Magni can sound very good with these phones, if you use the right DAC.
I do not think a very good amp will compensate for a bad source--at least not with these phones.