Matt, kissing gouramis grow very large, I'd trade them in for something smaller. The crayfish may hurt your fish eventually, they'll grab anything they can get a hold of. SD's get too large for a 20g (around the size of a salad plate), and as Crabbypatty pointed out they're best in a group. Unfortunately, with a 20g tank, there's not enough room to add more.
If you liked the rams you saw, a nice mix for your tank might be something like a small group of tetras, a pair of rams and a couple corys.