All fish other than true vegetarians are "predators" ... so anything in a tank at the pet shop that eats living prey would qualify there.
60g is about the minimum for your choices of either single Oscar or a pair of JD .... so the stocking issue isn't a concern (IMO),but the filtration is.
When dealing with larger "predatory" fish (translates as "messy" and high bio-load) you always IGNORE the "rated for xx gallon" rating on the filter and look at the ACTUAL flow rate in gallons per hour (gph). Especially with the cichlids you are considering,you need a MINIMUM of 600gph with power filters,300gph with a canister,or 450gph with a combination of the two.Anything less will require lots of high volume (or high frequency) water changes to maintain water quality and avoid other issues related to it.
Also,if considering "predatory" fish for the "feeder thrills",I'd advise against it ... very little nutritional value in feeder fish,risk of disease/parasites,and thiaminase content doesn't make it worth it. Not really even necessary for "piscovores" (fish-only feeders) like my Parachromis species.... which do great on a prepared pellet diet with insects/worms as feeders.
.... and for "predator" (other than cichlids),I like this guy http://www.wildwoods.co.uk/fishhouse/images/red-erythrinus-2.jpg
http://aqua-bonito.web.infoseek.co.jp/BIG/erythrinus%20erythrinus07.11-01L01.jpg
Red Wolf Fish (Erythrinus erythrinus) ... appropriate size for your 60g.
