Though I'd bring an update on my completed mod.
I would like to first thank everyone who contributed to this massive thread and everyone who personally answered my questions and I apologize for not remembering all of your names on top of my head.
My mod was successfully completed a few days ago and I thought I would do a short mini-guide just for the sake of saving some time for new people interested in attempting it and not going trough the whole 160 page thread although I would recommend going trough a good chunk of it as I bring nothing new to the table and merely repeating what others have said before and even the idea of my radiator placements was taken from another poster who happened to have the same case as I did.
The mod was done in an 600T case with :
2 X 7950 in Crossfire ( 1 Sapphire , 1 Powercolor)
2 MKII bracket sets from Sigma_cool
2 Antec Kuhler
Extra EK shim (Sigma_cool kit will includes shim)
I usually do not take photos of what I do but since I did both my cards a week apart from each other I took a few as reference
You want to first start by unscrewing all the screws that hold you current stock cooler and unplug the fan power cord then you can slightly wiggle it and it should come right off. Clean off the thermal paste on the dye with rubbing alcohol until it's sparkling clean with anything that won't leave lints.
The Antec Kuhler 620 or any cooler will generally come with pre-applied paste but I chose to use my own, trick I've learned from the thread was to simply push all the paste in the center and wipe it off with rubbing alcohol again as simply wiping it might leave some paste stuck in between the screw cracks if your clumsy.
Next I applied thermal paste on the GPU dye and sandwiched it with the shim on top which I've covered with another layer of paste, I'm not gonna lie I don't know how much to really apply, simply went with the more than the cpu approach and made sure to leave no thin spot where i could still see the copper shim ( not finished in the picture)
Now the bracket and cooler installation was the most annoying part for me to get right as the shim would keep wiggling around and I would have to unseat the cooler and realign the shim several times, a second pair of hands will definitely help here or if you have an EK shim which I have used on my second card which made it WAY easier as the shim is larger in size. you will want to have the tubes on the opposite side of where you would insert the card. I've followed the recommended advice to tighten the bolts by hands which is enough by itself ( Give it a good amount of force until it won't go further but don't force it beyond that.).
Just a picture of how it looked after completion. I would generally install the heatsinks before slotting the cards in but I haven't received them at that time, my sapphire card came with a heatsink covering the VRAM and VRMS which was very convenient
Full completion except for the big mess of cables
Overall I am very satisfied of the results, the fact that it is so much more silent alone is worth it to me and temps are just amazing compared to before of which could hit around 85 degrees at full load on stock clocks. I'm running both cards at the moment at 1150/1500 and depending on room temperature temps at idle are 24-30 for both cards and 60-65 at full load for the powercolor and 45-55 for the sapphire. VRM temps seems to stabilize for both at around 59-67 degrees. I did add 2 side panel fans blowing on them. Interesting fact, with the way I've aligned the radiators it was actually possible to seat a fan under each card blowing on the VRMS using only the tubes to hold them in place but I didn't want to risk the off chance of bumping my case and the fans getting caught on a capacitor.