If you are still talking bout 50 gal tank, No the Kissing Gourami would grow too large.
Many of the Dwarf gourami are prone to Viral infections (See Dwarf gourami disease) which are said to be untreatable,possibly infectious,and usually result in death.
Honey gourami might be option for your tank, They stay relatively small, and aren't as prone to disease.
Single Pearl gourami might also work depending on number's of Angelfish.
Do keep in mind that nearly all Gourami are a bit territorial, so placing more than one or two in large tank, can often result in one or more getting picked on for there is not enough surface area available for them each to have their own space.
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