
Multiple Spawning With One Teleport
I used a trick in apdm3 to spawn a lot of knights near the end by using a little trick I developed because I couldn't be bothered to make 8 or 10 or whatever teleporters to spawn them.
If you create a tall spawn room with a thin teleporter at the bottom and stack the enemies on top of one another so that only the bottom monster is touching the teleporter you can teleport them in (obviously always to the same location) in the sequence they are stacked.
It's a good trick for ambushes but you need to trigger the next monster in the stack to wake up before you trigger the teleporter or it won't drop down into the teleporter.
Anyway, if you want to save on entities and hassle for big ambushes and think this might work, then it might be worth having a look at the map source (included with the bsp) which is available here:
http://than.quaddicted.com/files/apdm3.zip
if you are that bothered about the monster wake up sounds, you could always have a small hidden door located near the teleport destination that is triggered as the monster spawns and uses the monster's wakeup sound as its move sound. Bit of a faff of course, and not worth it if you have fewer than 3 monsters.