I have the IM 25 lagoon AIO, as well as a couple each of their 10 gallon and 15 gallon AIO's, they are solid tanks for sure!
For my 25 gallon, I swapped one filter sock for a media rack, which I prefer to socks. On the other side's first chamber I have the IM 9 watt UV, but I don't run it often. I set one of the 'fuge chambers up with a 'fuge basket and loaded it with live rock rubble as something of a "cryptic 'fuge", but it's not clear if that's really beneficial or not (at least to me). The other side holds my heater.
I've replaced the stock pump on my 25 gallon, I've run it with both a single IM Mighty Jet 538 gph pump, as well as with two IM Mighty jet 326 gph pumps, which is what I'm running currently. The return pumps from Jeabo also work very well, and are less expensive than the Mighty Jets.
And, I went with and really like the Random Flow Generators from Vivid Creative Aquatics. These replace the stock return nozzles, and create a nice, random flow all on their own. If you're goal is only easy soft corals, this may be all the flow you need, but since you have it, I'd also run your gyre.
You can see more of how I set up my 25 in the link in my sig.
I hope that helps and good luck with your build!