I've got a reef radiance 155 over my 40B. It's last year's model, but the new models look great and are apex controllable.
You would probably need 3 of them over the 120 - depending on what corals you intend to keep - but they're well built, affordable, and I've been very please with my LPS and softie growth in my tank over the past 8 months. No SPS, so I can't comment on them if you are going for an SPS tank.
They're a sponsor of R2R, and there are some threads about their lights if you search the forums. You'll find many others with similar opinions.