Had to postpone the second HD 6670 for several reasons, one of which was that an Asrock Mobo under my Intel Quad died.
Replaced the DDR2 board with it's DDR3 nephew from Asrock, and upgraded it to 8Gb. Still cheaper (at some 83 Euros) than
upgrading the original DDR2 board to 8 Gb (some 128 Euros), which shows you how DDR3 RAM prices have gone south, while DDR2 went north.
The other reason is that I could acquire a second FM1 Mobo for my temporary laid-off A6-3500, a Gigabyte A75M-UD2H.
As 2133 Mhz memory with decent latency has become affordable, I will try that in the new set-up and try to push the A6-3500 to its limits.