If this was a few years back, you wouldn't have all that much choice, but nowadays there are plenty of skimmers which could fit your bill at about the same price point of the Vertex IN-100.
The Vertex isn't a bad skimmer at all. Its issue, as mentioned, is the Resun pump. The first series of Vertexes had issues with their needlewheel impellers cracking and sometimes fusing. I know Vertex has attempted to address this issue recently.
IMO two of the best bang for your buck skimmers now are Bubble Magus and SWC, both of which use more reliable pumps than the Resun.
Bubble Magus skimmers are direct and shameless knock-offs of the Bubble King Mini skimmers. So your getting the same design of a $1,000 German skimmer for around $200. Of course your not getting half-cm thick laser cut cell-cast acrylic or titanium screws or a butt kicking Red Dragon pump, but your livestock probably won't notice much difference.
SWC skimmers in your price range use Sicce pumps. These pumps are quite touchy when people modify them in meshwheels but they are generally quite reliable when left in stock needlewheel form. I believe that SWC skimmers are also made in Canada to boot!
BM and SWC also offer conical skimmers in around the same price range which are the latest in skimmer fashion. I'm not sold on their supposed superiority but they sure look pretty cool.
The ETSS Reef Devil is a good skimmer. As a downdraft skimmer it works in a different way than needlewheel skimmers. The issue with the ETSS is that it requires a fairly large pump to operate. The manufacturer recommends something like a Mag7. Mags are infamous for their ability to suck electricity and heat up aquariums. I had a smaller Mag3 running an old AquaC Remora skimmer in a 46 gallon tank. I didn't need a heater during winters and I could not run it more than a few hours at a time during summer months or it would overheat the tank. In comparison to a Sicce or Atman needlewheel which use around 25-30W, a Mag7 is rated at 60W. That can add up over time since most people run their skimmers 24/7.
Another option is to look for a used EuroReef skimmer. The basic ER design - needlewheel pump next to an acrylic cylinder - has been copied by numerous other skimmer manufacturers (including Vertex). I ran an old ER CS-series skimmers for years. The problem with the older ER skimmers were the Sedra pumps used on lower-end ones. Like Resuns, Sedras would sometimes shred their impeller magnets over time. Consider it a big score if you can find a used ER skimmer with an Eheim pump.