Well Rock On, I will give my opinion also. In the past year I have run an Eshopps 150 PSK, BM Curve 9, Omega 150, Reef Octopus Classic 150.
The Eshopps 150 for the Money is not a bad skimmer the cup is small and no drain plug fills quickly empty every day but thick stinky green to black goop.
BM Curve 9 Kicks butt one heck of a skimmer. Large could fit the Omega inside it, my unit was a little noisy so I was waiting for a new Impeller. I have heard the 9's are loud because of the larger pump but 5's and 7's are quiet.
Vertex Omega 150 well got this because they did not have the RO 150 in stock and was told everything else is junk BEST SKIMMER on the market right now. Ya right did not impress me skim that was produced was always light in color and sometimes pretty much clear. The Turbulence in the skimmer I believe is excessive and I believe the pump is to much for the body size and shape I think the foam rises to quick and not enough contact time which would explain the light color of skim. Anyhow after spending 400 plus on this skimmer I can not recommend it save some money get something else. I will say it is quite to run.
Reef Octopus 150, Love it if I did not have one I would not believe how well this skimmer works, it has truly stun me how well it works. Basic to the point no BLING BLING like Titanium screws and a Cup you can use a weapon if some breaks into your home. It produces lots of foam thick and the color of the skim is dark green to black and stinky! It is also as quite or quieter then the Omega believe it or not. I paid 248.00, I know you guys south of the boarder should get it a bit cheaper but for the money the performance is outstanding! I also think its one of the only RO that can run in deeper water levels I have it in 8" and the instructions say nothing about having to have return above water. Mine is under. Another quick note is the gate valve much easier to adjust then the pipe that the other 3 have.
So bottom line I would say go with the RO Classic 150 not Space Saver and my second would be the Curve 7 I believe for the money you can't go wrong with either.
Just another little note all the skimmers above where bought brand new, not used.
Good Luck on your choice and I can not comment on the other skimmers mentioned just on what I have used, well almost there is my Becket Skimmer but that's a whole new BEAST.