My current rigs are as follows:

Rig1:
2x Diamond 7970's (750kh/s each)

Rig2:
4x Gigabyte 7950's and 1x XFX 7950 (625kh/s each)

Rig3:
5x Diamond 7970's (750kh/s each)

I managed to lock in an unbelievable price on 5x new R2 290's and am waiting on them to be delivered. As we all know, stock has been an issue for some time now!

Also have two MSI 7970's which i'm trying to find the right config for as they are proving to not like my current 7970 settings. The trial and error continues on that front!

2 of my rigs were self built and can run 6 cards. If you are thinking about building rigs like this, they aren't particularly hard to do... but make sure you have solid parts (i.e motherboard and PSU's). Don't be cheap on these things! Quality is key if you want consistent and reliable results.

~Bundaroo