> I also like the four head X1XXX based FireMV 2400 (again, not supported).

The FireMV 2400 (which besides PCIe x1 also comes as PCI version btw) has the RV380, which is X600, not X1xxx. But as the question was about a PCI card that's already supported (in theory at least), the FireMV 2200 PCI with RV280 would be more apt.

> One of those in the X1 slot and something similar in the PCI or PCI-E X4 slot

Using the PCIe x1 slot disables onboard SATA, so you'd need a SATA card in the PCI slot, which only leaves the PCIe x4 slot (with x16 connector).