The Bolivians are great centerpiece fish and they get along with just about everything. You'll definately love their UNIQUE personalities! They're a blast to watch when they play. Mine used to school with the lemon tetras...
HOWEVER...if they decide to spawn, your cories will be in for a rude awakening and will most likely be the victims of the rams protecting their eggs. There have been MANY reports of One-Eyed Cories after a Bolivian Ram Spawn. just use caution.
If you want to keep the cories, then you'll need to monitor for aggression from the rams. Alternatives for cleanup crew would be ottos. you'll want prolly 10 or so for that size tank.
The BN should be fine, just make sure you have at least some driftwood if possible. gives them a place to hide and an alternative snack if they want it.
The tetra population...
Cardinals are a decent choice, but I actually prefer some of the other tetras out there.
-Lemon Tetras are AWESOME and are a brilliant yellow when happy.
-Blackskirts are another good mid-tank tetra. They have a similar shape as Angels but are much more mellow.
-Serpae Tetras(Or the Longfinned variation) can display a stunning Red color.
-Penguin Tetras are a nice variation as they're not as common as some of the others.
-Hatchets:
Marbled are nice and do stay a little smaller, but the Silver hatchet is actuially a much more hardy species. Hatchets do require a good lid because they're jumpers and also, they like a bit of floating cover. floating plants are good for them.
Overall, here's one possible variation to what you have and the cardinals can stay since they were there first.
2 Bolivian Rams
6 Cardinal tetras(the ones you currently have)
6 Long Finned Serpae Tetras(the red ones)
10 Lemon Tetras (for the flowing yellow)
6 Silver Hatchets (for the top)
1 BN Plecco (for cleanup)
Also, is this a planted tank? If you want a TRUE SA system, I can recommend a list of SA Specific plants for you as well. if interested in SA Plants, please PM me and we'll get ya all setup.
PEACE!
-TF