116 might be way better then 2 58s. Could be wrong but the way I understood it there's a huge advantage of multiple bulbs in a single unit as opposed to several single units.
If you're at 474 watts for 3700-4000 gph you could do lots better..... Wlim does pumps, Reeflo and Dolphin are also good ones..... For externals anyways. For these you're gonna have to drill, unless you're down to go bigger and acrylic
For socks if you're at 200 and 7x16s and they're plugging fast you must have some serious stock! lol How many socks are you running? I was gonna suggest some sewn together socks as they seem to last a lot longer then single micron rated socks, but they start at 200/100 and go down.
Could always rebuild the sump and use more socks..... Would make changes last longer. Maybe 4 socks and stuff some 300 microns in the 200s. 2 sets would allow a quick change out and you'd have time to wash the others. Maybe some porous sponges before socks, or even brushes. Moving bed media for bio is some pretty crazy stuff.... Wish I would have went K3 over K1.
Wlim does make some crazy nice bead filters too....
Can't wait to see what you come up with!!!