For a 73 gallon tank, I recommend two AC110s, for a total capacity of 220. This may seem extreme, but a single AC110 won't give you twice your gallonage in filter capacity.
As soon as your tank is stable, I suggest you remove the carbon from both of these filters and replace it with an extra bag of biomax in each. You really don't need carbon unless you are trying to filter out medications or other toxic chemicals. Carbon is chemical filtration, and it stops being effective after about two weeks. You'd benefit a lot more from the extra biomax.
I also suggest prefilter sponges on the ends of the intake tubes, which can be piggybacked for deeper tanks. These will catch a lot of debris before they can enter your main filter, and will keep your media cleaner longer. Also, the prefilters will help prevent tiny fry and small invertebrates such as red cherry shrimp from being sucked up into the tubes.
If possible, try to seed your new filters with media from an established (stable, already cycled) aquarium. Doing this will help to instantly cycle the tank. Also, add Seachem's Stability, a bacteria booster, for the seven-day regimen they instruct on the label. This should help to quickly build up the beneficial bacteria (biofiltration), and you can add fish right away. In fact, you must, or the bacteria will have nothing to feed upon and will die.
The AC110s tend to be a little noisy, and because they're large, they may seem clumsy to work with, but it doesn't take long to get used to them, and they really do a great job. The only problem I have with mine is that the plastic lids were warped when I got them, and I really have to hassle to get them to seat properly onto the tops of the filters. That's just because they use cheaper plastic these days, and there's more surface area to warp. But it's still well worth having these filters, in spite of this minor inconvenience.
The other thing is to adjust the levelors so the filters sit straight and level on the back of the tank. They'll work best that way.
Good luck. Do you plan to give some cute little dojos a new home? If so, keep their water temperature no warmer than 75F, as they are cooler water fish. You won't need a heater for them.