the biggest thing about what your considering is the size of the frogs and their territoriality. they are small! VERY small. and most (that ive seen) seem to have a subtle mixture of blue and red. making them blend in pretty well. a 160 gal tank with 3 frogs that are tiny and blend in well, may end up being something your not as interested in, so its something to consider.
now about the frogs specifically, they are a frog that comes from a small island in the bocas region of panama (as most pumilio do), however there is a continuing trend to classify them as a distinct species. so not pumilio at all. they are often referred to as Oophaga sp. 'escudo', this along with the fact that they are an obligate egg feeder, means that they are priced pretty high. that price has dropped some in the past year with the newer imports but still remains pretty high. i would expect a trio to go for $600+
i would personally suggest a more colorful and larger frog like almirante/ MC, or bastis, el dorado, christobal, nancy, etc. OR a large colony of ranitomeya. something like fants could do well in a large tank and you could fit many more in it than pumilio (comfortably and with minimal stress)