You might also look at the UM3X. I haven't used the W3 but have used the UM3X and have used the IE8, TF10, and SE530. From information I've read, the W3 offers more of a V type frequency response while the UM3X is flatter. The IE8 is a relatively flat response short the few dB bump on the lower half. It's hard to say if the W3 or UM3X might be a closer fit simply because I don't know how much they vary.
The IE8 offers a lot of good things. One, it's bass extension is bottomless and does not drop negative in sensitivity throughout the audible spectrum. The sound stage is big and spacious, more so then pretty much everything else out there. The sound is decently natural and pleasant to listen to. It does need an aggressive enough burn in and good wattage pushing it to get everything out of it. It likes power and it's a little tight until you really push it.
The IE8 in my eyes is largely flawless. There are matters of personal preference, but it doesn't inherently do anything absolutely wrong.
What can you gain going away from the IE8?
Relatively speaking, the IE8 is slightly soft on edge. You are capable of getting earphones with sharper detail and more dynamic range. The IE8 isn't exactly tame and velvet smooth though. It really is middle of the road.
The big stage size makes the experience less intimate. You are more sitting in the grandstands instead of up on stage. Part of this also limits the ability to produce solid locational cues and layering. Everything is far away and there is minimal distinction of distancing. Other earphones can make for a more intimate and forward experience and provide a greater sense of distance and layering between singers/instruments on the stage or recording studio. The stage space won't be as spacious though.
Is the bass too much? It's certainly nothing a few dB EQ cut can't fix. The bass knob is a joke though. Sensitivity gain starts at around 800Hz and peaks at 100Hz before rolling off again. The knob ONLY affects frequencies below 100Hz. You set the knob low, you lose all your bottom end and get an anemic bass response but still midbass emphasis. The knob all the way up produces an even and extended response down to 20Hz easy with the slight peak at 100Hz. The best route is bass knob full but with a small wide EQ cut centered at 100Hz. That pretty much fixes the only real "problem" of the IE8. I can't really say I've used another IEM that's done low frequency information as good. Something like the UM3X or W3 can produce similar results with more dynamics, edge, and energy though but also a completely different presentation overall. In terms of raw capability, they're similar, but the IE8 has a very slight edge on raw capability. The W3 probably has an edge over the UM3X because it was specifically geared for more bass and treble. I would say choice for bass is a matter of preference.
What about the treble? Well, I personally find it to be slightly soft. It's extended and sensitivity is there up to above 15kHz without a problem. However, the soft edge on details remains constant through the treble. This for some might be a hair tame on detail and crispness. It's simply a personal preference thing. The W3 supposedly has a pretty detailed and sparkly top end. The UM3X is more tame with a slight lower treble bump(likely dependent upon tip choice), but I wouldn't call it sparkly.
I don't think any of the earphones would be bad in the midrange. The IE8 has a midbass emphasis but largely flat. The UM3X is relatively flat with a slightly lower treble/high midrange bump. The W3 is more V shaped probably with a little more emphasis on the extremes.
In the end, should you step away from the IE8? Well, that depends upon what you want different and how much you are willing to let go for something else.