> Then I was misinformed about the FireMV 2400

Maybe you confused it with the FireMV 2200 PCIe (x16), which has the RV370 and would thus be similar to the X1050.

> The FireMV 2250 PCI could also be interesting.

I was not aware that there is a PCI version of that card, just PCIe x1 and x16.

> I am, however, confused as my info list the FireMV 2250 as an RV516 GPU.

This seems to be correct. FireMV model naming seems even less transparent than for normal Radeon series.