Anyway, I do use the PSU switch as well and after a few times of trying it recognizes all 4 gpus. I don't use a display usually, but when connecting one sometimes it doesn't even show the boot/bios screen?!? And sometimes though the screen works, but when starting X it again crashes:
20.484] (WW) fglrx: No matching Device section for instance (BusID PCI:0@0:0:0) found
My situation is not as bad as yours. I have three nearly identical rigs and one of them, sometimes needs more than one power on/off sequence, and a reset, in order to properly recognize both GPU cards. When I first set up these rigs I was mislead because the poclbm miners would start fine - no errors, but proceed to use all the CPU at a low hash rate. I speculate that this is because the miners can recognize the CPU as a device and I speculate that somehow the CPU is emulating the GPU and running at a much lower MH/sec.
Eventually I used aticonfig to display the recognized adapters, and rebooted until they were all there. As I mentioned in the post above, I use a UPS to avoid reboots. The miner rigs run for days, and I reboot them only to upgrade mining software for example.