Nothing which is as good that is also portable.
The Q701 doesn't really work well with poor sources, a portable amp works best with a line out signal (not a headphone out signal).
For your PC and phone ideally you want a DAC/AMP like the Fiio E17.
Personally I would not use Q701's with my phone, If I want to listen to music I use my PC. The Q701 isn't a portable set of headphones.
e.g. I have HD25-1 II and Momentums which are my portables. I plug them into a topping NX-1 which is fed by a Fiio LOD which is plugged into an old ipod touch.
HD558, Q701, HD600 and HE400 are strictly for home use only with either my xonar DG, mixamp, Aune T1 or Vali or a combo of those.
In your position I would simply forget plugging them into a phone and buy a decent DAC/AMP or sound card for your PC.
How do you find the Q701 compared to the hd25's?
I have the same setup as you (ipod, lod, topping, hd25) but am looking for something with a wider soundstage.