I think when you're going with gouramis, it's the luck of the draw. I owned a pair of dwarfs and one killed the other. If you do get a pair, try to get them as close to the same size as possible. This hopefully will reduce the chances of one turning in to a bully.
Oops, forgot to mention, angels aren't necessarily that aggressive, usually a mated pair will display very territoral behavior esp. when there is a spawn.
It was in fact, my dwarf flame gourami who was stressing and harrassing a large pair of angels I had and I ended up removing him from the tank.
i agree with the honey gourami "luck of the draw," as each fish has its own personality, and even females can be agressive toward one another. i think you should go ahead and get the angel, because i have found that they do fine by themselves and cause no problems.