The bubble magnus NAC3 and SWC120 cone both use the atman 1100. Both pull similar air at around 250lph. The SWC120 cone is a cone and better design. The impellers on the two are similar but the venturi on the swc is better, and it also has a bubble plate of good size. The build is much sturdier and the swc has a easy way to adjust the water level in the skimmer. It also has a fitting for the neck unlike the bm skimmer in which you shove the neck inside the body and use a oring to seal. But the BM is cheaper price wise.
The bubble magnus NAC 6 is like the new SWC Budget skimmer coming out. The NAC6 pulls 500lph air compared to the swc which pulls 700lph air. The swc is better built, better water adjuster, and a true connection at the neck as well as a bubble plate which is large enough. The pump is the same, atman 2500, but the impellers are different as well as the venturi. Both are quiet skimmers, the SWC is priced $5 cheaper.
The BM NAC7 and SWC 160 cone are similar in size and both use the same pump. The swc pulls 700lph air compared to the NAC7 which pulls 500lph air, due to the impeller and venturi. The BM impeller is mostly mesh were as the swc impeller is 90% nw and 10% mesh. The venturi makes a huge diff between the two. The build quality is more solid on the swc and there is a better transition on the swc along with an actual neck connection. The neck diameter on the swc is smaller as well. The water adjuster on the swc is much better as well. The bm is $25 less though.
Other skimmers you could look at is the SRO1000 or xp1000 which seems to be a nice skimmer. They are inbetween the swc120 cone and the new swc budget skimmer or nac6. It pulls around 400-450lph air and is around $80-100 more than the swc budget or nac6.
For that size of tank i would go with the sro1000, NAC6 or SWC budget skimmer. It would be a good match. I don't think you can go wrong with any of those myself. One thing i forgot to mention is all the swc skimmers come completely apart. I never thought that mattered much but it makes it extremely easy to clean.
*And yes i have tested each of these skimmers on my tanks but I only sell the swc's : )