I'd rule out the chevron. They lose those awesome juvenile colors as they mature and get quite large. Now that you say that your 125 is a 4 footer, I'd reconsider a tang.
Mines a 6 footer and the Tomini flys from one end to the other in no time.
I've never had tangs in anything less than a 6ft tank.
Hmm...that's disappointing to hear...
Would the One Spot Foxface do ok in a 4ft tank then? Does it have the same algae eating power a tang would? LiveAquaria says they require a 70gal tank at minimum.