Neither cooling supplied with 7950 is good enough. Simple as that. Without 120mm fans there is no hope of expelling vast heat mining produces (I wrote a post some weeks ago comparing 2x120mm cooled GTX580 TF3 @65C and 2x80mm 7950 TF3 80C core + 85-90C on VRMs
).
Excluding prohibitive liquid cooling for mining, by few galaxy lengths best option to cool mining 7950/7970 is Prolimatech MX-26. You can chop, just like that, up to 25C on core and up to 15C on VRMs [vary on airflow and other stuff].
Of course there is an issue with voiding warranty and 3.5/4 slot size cooling, but that is best choice. Tested few 7950 and ALL sound like jet taking-off. Useless 80mm fans. I don't know which magician (no matter MSI/Gigabyte/ASUS/etc) thought that using 80 instead of 120 is good idea, but there you are...
Just like HellDiverUK getting rid of VGAs. Even when compared to tiny USB Block Erupter all VGAs are just hopeless. Looking at local prices and for a cost of one MSI TF 7950 I can get 4 USB BE - ~500Mh/s@175W vs 4x330Mh/s@12W total. No-brainer.