I may not be for you, shotgunshane. The FXZ100 is not fatiguing to me at all. It actually sounds more like a headphone in my ears than a earphone. But I sit here and try to describe the sound all day, but truth is until you hear the earphone yourself you can't get a true sense of the wonderful technology JVC has come up with. This bass, while more in quantity, is not your typical overly-bloated boomy bass. It's not like "boom boom boom" and then there is the mids and highs. The bass is somehow integrated smoothly with the rest of the sound spectrum. But if you like neutral sounding or bass-lite earphones, these are not for you. If you can stand the bass of the Aurisonics, you can stand the bass of the FXZ100 (I can't comment on the FXZ200 as I haven't heard it yet). If you can stand the quantity of bass of the 1964-Q, you can get along with the FXZ100's bass. Now, the Sony XB90 had too much bass for me, and I would say that the FXZ100's bass is not on the level in quantity, but surpasses that Sony in quality. From what I'm read, the FXZ200's bass may be on the same level in quantity as the XB90, but I'm still interested in hearing the 200s as it seems that bass is better integrated with the other frequencies than the XB90 is.
But this may not be everyone's cup of tea. For example, I recognized the superior technical capabilities of the Sony EX1000, but I could not get along with it because of it harsh piercing highs. Some members who I know have similar taste as I in IEMs part ways when it comes to the EX1000. So yes, this JVC has serious bass, yet it's bass like you never heard before, especially in how it's integrated into the whole sound. You don't like quantity and quality bass (or aren't a basshead), look elsewhere. But if you could love, for example, the IE8's bass (but wished for a far superior bass), this JVC would be for you. And this earphone doesn't sound anything like the FXT90 (which is mostly mid-bass) with extra sub-bass. It is uniquely tuned and set apart from the other JVC IEMs.