So far there was only one card which supported 6 monitors at the same time – Radeon HD 5870 Eyefinity 6. It featured support for 6 monitors running at maximum resolution of 15360 x 9600 pixels. Such resolution required lots of memory capacity. Radeon HD 5870 has 2GB of GDDR5 memory, while HD 7950 has 3GB, which is obviously enough to handle such a demand.
AMD is also preparing another variation of HD 7950 with 1.5 GB of memory. This would result in three variations in total. Radeon HD 7950 Eyefinity 6 Edition will likely be the most expensive of them. However the price in not yet known, so is the release date.