90% of graphics card sales comes from "GF4mx-range" cards. Based on that, even regular sli setups of today are a niche market. The only reason why they are doing 2 cores on one card is because they are the much higher yield 6600 cores which they have much better, cost efficient success rates under manufacturing for. Therefore, a 6600 dual card costs less to manufacture for a company like Gigabyte then one 6800u card.