What we learned from the release of the Lightning and the Super Overclock card still applies for the Matrix, apparently. The reference cards are fully capable of handling the R5870 load on air as well as their custom PCB brothers resulting in at least equal if not higher clocks. These custom cards can have their benefits, but only on liquid nitrogen and only if the GPU on the card is great ...Sometimes I think we expect too much.
When the Matrix Platinum was first started to break out of the ASUS labs a, admittedly very specially selected model, managed to obtain 1500MHz on the core. Of course we'd never hope to get near that on a retail model, but nonetheless we were hoping for perhaps 1150+. Certainly with the myriad of overclocking features available and with this board currently an eye-watering £408 we were hoping for more than 1050MHz with a stable of just past the 1GHz barrier. Most of the "specialist" cards we've seen will do a GHz happily and for a fraction of the price.