What result do you want from your system? More bass? Cleaner sound?

I actually think you should be careful with going to the 8000s - they are tremendous speakers - but they can put out A LOT of bass. Usually thats a good thing but depending on your room, you might really need to control it. The speakers do have the boundary settings built in which will help, but the best way to get results out of them in my experience is the MRC. Given that you already have the 7000s on the fronts and the 5000 series HC speaker (the 7000s are supposedly close to those in terms of performance), your front seems pretty well matched. Going with 2 8000s could highlight the difference between them and the HC speaker.

My vote is to go in stages and go with the v4 with the MRC. Then see how you like it and then when the upgrade bug hits again in a year or two go ahead and get those bad boy 8000s. Maybe a year or two later you look for a 7200HC and then you move the 861 to v6.

When you get MRC be sure to turn off the boundary controls in your speakers and then run the MRC. See the wiki for hints and tips.

Best regards,
Jerry
Main System: 861v6, DSP8000s in corners, DSP7000s Center and Sides, 1-9 humans.