Good morning Adehner.
Do I understand correctly that you want to cool both at once with an Eisbear? Unfortunately this is not possible in the configuration, you would need a second water block for the graphics card. Since there are no full cover blocks for the V7900, you would need a universal block like this one:
http://bit.ly/2voU22O Then you would have to provide the voltage converters and RAM chips with small cooling plates so that they don't overheat due to lack of cooling, like this:
http://bit.ly/2uMFExE . All in all, it would not be an elegant and simple thing to do.
Another option would be a separate small all-in-one cooler like a NZXT Kraken X31 (
http://bit.ly/2uu58oa), equipped with a NZXT Kraken G12 adapter (
http://bit.ly/2uMAuBH , unfortunately not available at Digitec), which has a small fan built in to cool the voltage converters and RAM chips. But I can't 100% guarantee that the Kraken adapter will be compatible with your V7900, older FirePro cards are always tricky about that...
Hope I could help at least a little bit.
LG Tamerlan