a fiio amp will not work with wireless headphones and wireless headphones in general are going to have less output than is capable on wired models simply because they have no directly connected power source (they run on batteries).
imho the sony XB headphones are crud not worth looking at. sure they do offfer lots of bass however it is so muddy and distorted (not to mention everything else is so distorted and muddled) that it completely ruins all sound which comes out of it. i bought a pair years ago to try out and they went back the very next day. horrible. yes, they do provide plenty of bass however is it really worth bad sound? if you want the absolute heaviest bass though for $100-ish the XB line is about as good as you are going to get but will sound like crap.
if you want clean bass and still have a low budget of $100 i'd go for a pair of ath-m50s. while they arent as bassy as XB headphones they are still not bad at all and do have pretty much the best low end you are going to get without muddling the whole rest of the sound stage. you could amp them for a bit more performance or tune the eq accordingly as well. i personally use a pair for such things as dubstep (which if you know bass... you know is just about the most bassy music which absolutely requires good bass to sound good) and they sound fine to me.
if however you want the most bass possible at the expense of everything else there isnt much you can do but buy xb500 or xb400 from sony. they are much much more muddled and sound like crap but they do have lots of bass.