Using Plextor PCIe M6e SSD Drive in Vostro 230

Vostro 230 has one PCIe slot which I currently use for a video card.  Since I'm  not a gamer, I may replace the video card with the new Plextor PCIe SSD which is the first SSD to fit into an open PCIe slot.  If I were to connect a standard SSD to a SATA connection, it would run at only 3 GB/s instead of 6 Gb/s. If the Plexor SSD is connected to the PCIe slot, will it still run at only 3 Gb/s instead of 6 Gb/s capability?  I believe this is a motherboard limitation but I'm not sure.