ok, I have wp 6's with BAT/vk50se and vk75se. Personally, I'd max out the 2 channel first. Maybe add Wilson's watchdog sub and upgrade the vk6200 to vk150se's. Then add the watch surrounds. Maybe keep the 6200 to power them down the road. I'd keep the 51se for 2 channel and run it in pass thru mode with a surround processor of your choice.
just my opinion...
just my opinion...