Watch out, and take care. I had those ones too. It was called "crystal ear" in lack of better description. The balance system in inner ear is thrown around by the calcium crystals being thrown askew in line with gravity. They are aligned up wrong. This can be cause by too loud or - actually - too low frequency levels. I can't listen to earphones on domestic equipment (mp3 players, and the like) either, at home, when lying in bed. Standing up is ok, but as fast as I move out the IEM, earphones or whatever, it's no big deal. I can keep balance.
Actually to get them in place again, is only done by a very painful process. But if you're into it, going into a boxing ring with protection on, and a professional sparring partner will throw them in the right direction again. With the cost of a broken nose, or broken jaw perhaps. Not kidding, but just severe traumatic impact may alter them right again.
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A small combo at 12" and above 100W with direct out possibilities, will get you covered. On top of that buy any of the D.I units out there just in case. In case you're subject to onstage monitoring, I would love to have wedge monitors with at least 15" in them. The 12" shows their sortcomings too often I think. GK has a brand new D.I in line with built in tuner, that has JUST been released. Other brands Tech21, EBS and Ampeg scambler DI are worth considering. But don't rely solely on D.I. Buy a small rig too.