i owned all three at the same time; i loved my sm3 and ie8, but disliked the fx700... tried hard to like it but couldn't find any redeeming quality about.. definetly overhyped i swear.
happy to be rid of it... especially bad seal that leaks so bad it affects the sound... and the bas is excessive, boomy... i had my brother listen to it... blind test and he preferred tf10, sm3 over it.
i also had a friend test it, and he wasn't impressed (preferred sm3)
fx700 top tier with the likes of sm3?? (utter rubbish imo)
Maybe you had some problems with the FX700, because I found them upgrading any aspect of the IE8 which I have also owned and liked. Or you have not tried the right tips for them. In my opinion the FX700 are one of the most musical IEMs and one of the best universals to date, but with stock tips they sound far from their best.