I had started off my journey with both dt880 and the q701 (both arrived within a few weeks of each other).
My impressions were that unamped (or at far as using an Asus Essence STX's integrated amp was concerned), the q701 (already bass ported modded) sounded somewhat reccessed (probably due to the larger soundstage), and more importantly, the treble was so harsh on some tracks that for a few months, I stuck predominantly to using my DT880s for everything. It had a more well-rounded sound signature that was suited for various genres of music, as well as movies and games.
I was rather disappointed until I got myself a new amp, a Littledot MK III, and I can safely say that the positions are reversed; I hardly used the DT880 in the last month. I don't have much experience with amps (other than a short while with a Bravo Ocean, wasn't impressed, and the one in my STX), but I'm guessing the trebles really mellowed out with the tubes, and the mids featured more prominently, and the bass presence is definitely not lacking.
With the same amp (tested on various gain settings as well), the DT880 while still pleasant sounding, sounds a lot flatter compared to the amped q701; I'm guessing where this was where the q701's soundstage really shines.
Strange how adding an amp in the chain changed my preferences between the two so much.
This is a kinda story to my own. I'm hoping my O2 is going to change things around.
I've been looking at tube amps & think the Q701 will be a perfect can for me once I pull the trigger. I enjoy my E17 with the Q701 but while not sharp or grating I can see how the mid range will benefit from the lushness of tubes. Have you rolled tubes in the Little Dot? In my main system I've been impressed with the amount of impact just swapping out some tubes will do. I'd be curious to hear everyone's thoughts on some tube amps with Q701.
I also thought this and was all set to order an LG 1+ but over on that thread the general consensus was that none of the valves it was compatible with sounded good paired with the Q701's.