Well, that’s a lot to consider. IMO, two pb1k will be better overall than a single pc2k. Adding a single pc2k could be problematic due to phase issues around the port tuning as they are different. This can be challenging and imo, a minidsp would need to be added and it can still be difficult. I definitely don’t want to discourage you but you should know it won’t be as simple as dropping them into place. If I was looking at something like this I would place a pair of pc’s in the front and try to incorporate the pb1k’s closer to the couch. Two pc2k’s will definitely outperform two pb1k’s by a margin so...if the goal is 2 of each, I would start as you suggested and just add the PC to the back. Then when you get another another one switch the pb’s to the back. Then look at a long term of four PC2k’s. That would be awesome! Hope I didn’t miss something, I’m still working on my first coffee!