[0-0]barts is a 6870 (with 2.5 sdk) and [1-1]juniper is a 5770 with 2.1 sdk. Both sdks working great together. Shouldnt be a problem to throw in mix 2.6 and others together.
It only works like that because of your situation. You can install 2.1 plus ONE of the following: 2.4, 2.5, 2.6 (havent bothered with 2.2/2.3, people say its cpu bug) because 2.1 installs into an entirely different path than 2.4-2.6. 2.4, 2.5, and 2.6 all share the same install path and, afaik, you can't install 2 or more of them since the new one will overwrite the old one (also the installer refuses to downgrade, have to 2.4 -> 2.5 -> 2.6, can't go backwards without manually uninstalling)