Payara and ATF are commable, but you must take into consideration that the tank they're going to live in has to be about 3 times their size.
Also depends on which kinds of Payara/ATF you're getting. Essentially, Hydrocynus Brevis is the best choice for ATF due to their FAR smaller max size as opposed to the others (Only 30 cm). Problem is, most Brevis' only come as accidental captures alongside VATF, so you'll need to consult one of the guys in the Characins forum for more detailed info. A VATF MIGHT work, but a minimum tank size of 8 feet x 4 feet x 4 feet is a must. One of the members here can attest to that (Heck, he even feels that it needs MORE room).
As for Payara, an Armatus will probably be the harder of the two to work with. However, a Tatuia or Scomberoides would make far better aquarium fish, seeing as their max sizes are far smaller (Correct if I'm wrong, but that's about 18 inches for Tats?). Just know that some people have experienced SDS (Sudden Death Syndrome) with their Scombs, so, again, refer to the Characins forum for more info.
Basically you can pull this off, but you'll have to get a FAR bigger tank first.