[R300]

Been running Rega Planet > Ben Duncan Phones01 > HD580J for nearly 15 years, but recently took the plunge on the K701.
 
Whilst the Phones01 synergises great with the HD580J, the K701 sounds a bit hollow, coloured and bass light. However my gut feeling is the K701 is capable of more (just based on my years listening to various hifi). I know the Planet is to my liking so this leaves the amp.
 
I've read here that amps from Burson, Graham Slee, Heed and the MF V8 synergise well, but would love to know what rigs people are actually using, and how they find the K701 performs. I don't really want to spend more than GBP£500.

 

[dex85]

i'm not going to answer your question directly, but imo the easiest and cheapest way to see if your K701 could sound better (not thin, overarticulate -> colored vocals and for my taste with overly pronounced details)  is to experiment with head-positioning. it makes a difference for me.
 
i wear the headband a little forward on my head and my ears are very close to the edge of pads. that way it sounds right to me, bass is there, vocals have very pleasing tone and intimacy to them (especially female vocals).if i put them backwards or straight up and my ears are in the center of pads, the sound becomes what i mentioned earlier + soundstage get compressed. everyone's ears and heads are different, so keep trying to find the best position for you.
 
you could try a different amp too, you obviously have done your homework, so give one of them a shot if you have the opportunity 

 

[Happy Camper]

A hybrid would be best for your budget. I agree with the positioning issue. I like a bit of tube bloom to fill out the body.
 

 
Extreme Platinum and CAL Sigma II DAC.
 

 
Laptop source setup in the family room.

 

[iittoo]

This is my simple setup for AKG headphones