I haven't heard the Thinksounds in a while but I am pretty sure they aren't worth the price jump from the Spark except for the whole eco angle. The Spark also has the advantage of looking like a more expensive product with its big box and machined aluminum shells. The only real concern I have with the Spark is that it's not exactly an upgrade from the S4 in comfort or cable noise (both are a bit worse when worn cable-down).
Not the same sig but the VSonic GR07 and HiFiMan RE272 can probably be considered variations on the 'neutral and balanced' theme with some minor caveats.
Entirely possible, I think some of the stores I used to buy these from don't even exist anymore. If you can spend $10-15 the Philips SHE3580 isolates pretty well (3-3.5 on the scale on the front page) and sounds excellent.
Thanks for the advice. I have narrowed down to the e-Q5, GR-07 and am looking at the Yamaha EPH-100. I don't really like the shape of the dual flange tips though. How do these 3 compare to each other?
I don't have the FX-700 now, but if I have it I might think that it's slightly bassy. And I do have the Ety HF5, which have slightly less bass quantity than what I consider as natural sounding. I am also looking at the RE-272, but I am just worried about the cable hardening issue on some of the Hifiman earphones.
I really would not recommend the GR07 if you're worried about treble fatigue.
The e-Q5 is overall brighter than the EPH-100 and generally sounds wider and more airy. The EPH-100 has significantly more bass and a bit less treble. e-Q5 bass quantity is still bigger than that of the HF5 but not by a large chunk.
The only real issue I have with the RE272 - and I say this as a fan of Etys and TWFK-based earphones that many consider bass-light - is that the bass ends up too far back in the mix.