Ceramic rings are great, but biochem stars work great as well for media to hold the nitrifying bacteria. I use the biochem stars as media for some drag in my DIY
reactor. Works fine so far. I think some of the XP3s come with the ceramic rings free, mine did so that is 16 bucks saved. The micro filtration floss is a great water polisher, so order some extra. Many don't leave them in all the time, but just put them in for a while to clean it up. I like leaving them in all the time and haven't lost a Dwarf Gourami since I switched to Filstars. (They need really clean water.)
PS. you can turn the spraybar back and run the water against the back wall if its too much current, but it won't be in your 90. Good luck. You've got some great gear to start with. I vote for the one XP3. You could always add another XP2 later if you want.
26 Gallon Planted Community, 90 Gallon Planted Community - Rena XP3, XP2 Filters, PressurizedCO2
, Eco or Flourite, TEK 4x54 T5 light, AH Supply PC