First off, that's BS. What do i need a freaking national aquarium to house a couple of fish?! Second, it won't be cycled properly. I got this fish for free off craiglist on the fly because the dude was going to let it go in a lake. It's not ideal i know but it's a risk that needed to be taken. Telling someone that you can only have 1 cichlid in a 75g tank without knowing what kind of filter is being used is asinine. The Canister filter im using on it has been cycled on a different tank and will be sufficient. 2076e Eheim, awesome filter so far, and two hang behind whisper filters. Unsure of the model but they each have two filter pads. I know i cant have lots of fish but at least two to three should be fine.........1 fish, pfffst.
To house a group of these fish? Yes, you need a freaking national aquarium (or big outdoor pond, which is how most Tilapia are housed). They are very aggressive - that means you need to spread the aggression over LOTS of other fish, or have LOTS of room so everyone can have their own territory. Put as many filters as you want on that tank, it's still only big enough for one.
Edited to add:
disregard everything below (but everything above still stands) - I just clued in to the fact that you said the filter you're adding is fully cycled - if the filter has been running on a tank with fish (i.e., with a bioload), then you're good to go, the tank should not even go through a cycle.
Luckily he's big enough to go for an extended period with very little food (i.e., just enough food to keep a very small amount of ammonia present). Treat the water with seachem prime every 24 hours (seachem SAFE is the exact same stuff, and would be a much more affordable option when treating that much water) to make sure the ammonia and nitrite are kept in their less toxic states and he should be fine. Make sure you don't let the ammonia go over 0.25 or the nitrites go over 0.5 (yes, fish can survive higher levels - but there's no justification for making them suffer unnecessarily).
Might be worth picking up some the bottled bacteria to quick start the cycling process - I know only some of these products work, and since I've never used them I'm not sure which ones, but hopefully someone who's used them will chime in. I believe you can get a tank cycled in a matter of days using that stuff.