I use the jebao RW range. The best thing about these, for me, is that they're variable speed. You can try a few different places in your tank on different speeds and just see what works for you.
I started off with the RW-20, the biggest in the range, in my 180g. Even on it's lowest setting it was insane. That one is now on half speed in my 360g, which is pretty good movement for keeping the bottom clean. I went with the RW-04 for my 180g but I have to have this one on full speed and to tell you the truth I still don't think it's enough. The RW-08 would have been better in my 180g, maybe on a mid range setting. I'll probably replace my RW-04 soon.
Knowing what I know now, if I got a 150g like you have, I think i'd go with the RW-08 and play with the placement and settings to see what worked best. But there are loads of other cheaper, and more expensive ones out there.