I'm assuming that ASUS would have provided a relatively long CrossFireX bridge. Otherwise if your graphic card manufacturer or ASUS hasn't, then you will need to find a longer one. For the majority of graphic cards, there is not a noticeably difference between 16x/16x and 8x/8x. The HD 4870 X2, HD 5970 and possibly GTX 480 will be the only cards which would 'see' a noticeable performance decrease. For example with HD 5870s, there is less than a 5% performance difference in average.