Well, most prefer the K7S5A. K7S6A Has 3 main differences from K7S5A:
1. SiS 745 rather than SiS 735
2. 3 DDR rahter than 2 DDR and 2 SDR
3. No LAN
It does have limited overclocking as well, but I haven't heard too much good about the ocing. I personally feel that the addition of one DDR slot is nothing to get excited over, neither is 745, and taking away LAN really sucks. Id rather have K7S5A