Get the caves ready but don't put them in the tank until you are ready to put the ram in. The gourami is territorial because he believes the whole tank is his, he has claimed it. If you throw some caves in it he will check them out and after a few days decide these are his too. But if you throw them in right before you release the rams into the water he won't know about the caves yet. This will give the rams a chance to claim the caves as their own. Same thing can be done if you just move stuff around. Moving plants or objects in the tank will throw off a existing fish's territory. Making it easier for new fish to claim territory. Last trick I have found that works pretty well is feed the tank while acclimating the new fish. Fish become aggressive when hungry, so full happy fish won't tend to be as grumpy towards new tank mates.
