builder Maingear is ready with the HD 4800 series, and you can now configure Maingear's gaming systems with up to four Visiontek HD 4850s or up to four Visiontek HD 4870s.
The combination of four HD 4870s will get you 2GBs of GDDR5 memory and will add US $1,315.01 to the price when compared to a single HD 4850 card. We would recommend a plain Crossfire with two cards, as this scales much better than four cards and it will raise the price by US $299.99 for the HD 4850 Crossfire and US $542.51 for the HD 4870 Crossfire, both compared to a single HD 4850 configuration.
As far as we could find, Maingear is the first system builder to offer these cards, and according to our source they have both of those cards in stock.
You can check out the systems here