E9 is $88 on Amazon. That's what I'd pick and I also own one. No idea why someone would spend the same amount on a portable amp for the Q701. I guess portable amps are more convenient.
Unlike some here, I haven't gotten them to sound good from many portable amps. The only way they sound good from my E11 and Total Airhead is if I use the headphone out so that they get more power from the internal amp. Straight from my E11 they're much more harsh and fatiguing than they should be. A lot thinner sounding. I still get enough volume to rupture my eardrums.
I have to say...Clip+ to Total Airhead with the headphone jack is quite good for the money! I used the Airhead with the K701 for 3 years back when I was new to all this and they didn't seem to have LOD cables around. I was fine with it.
If you get an E9, use the large jack. To pair with it you can buy an ODAC. That's what I use and it's a good match for the Q701. It doesn't make it more analytical/thinner or any of that nonsense. The ODAC isn't like that IMO.
Despite what some weirdos here say, the Q701 does not care about the 10 ohm impedance output. It doesn't even change with my receiver that has a 330 ohm output impedance.
I think the Q701 is fairly hard to drive. To me it's not as tough as the K501 or K400, but worse than the HD-650. It's pretty picky it seems with the DAC and amp. It HATED my Asgard. Wish I knew why...
K702 actually sounded better with the E9