He's not wrong, 7950's need high TCC's to perform well. High TCC's need more RAM. 8GB recommended. You can't compare to 280x's because they work on 2 threads with low TCC's.
Possibly, but they run fine now with gpu-threads 2 and intensity 13. TC doesn't seem to affect it as much as intensity, if I dropped intensity to 13 with 16k TC it started to work fine. I tried to drop TC below 6k with 18 intensity and did not work - HW errors.