SD-1 versus E-5....??
Sigma has a reputation for being slow to market, so it may be a while before we see the SD1 for sale. The E5 should be available any day now and you already have the lenses for it.
I have the E30 and the Sigma DP1s and DP2s cameras. The E5 looks very impressive, but if the SD1 is roughly twice the resolution of the current Foveon sensor that it should whip the wazoo out of the E5. I know the pixel count does not match up but I'd think of the SD1 as more of a medium format digital.
The dynamic range of the SD1 is likely to be far better too.
Of course, we still have a lot to learn about the E5! It will surely be a more usable camera, but the SD1 will be very compelling for its own reasons.