Highpoint RAID controller?

I can't say how it will work with SL, but on the '06 models, the EFI32 can cause problems.

As this model does contain EFI32, it might eliminate some hassles. I'm not a big fan of Highpoint, but their RR43xx series SAS RAID cards do work well, which includes the drivers.

With their other products, the firmware could be an issue (BIOS, not EFI).

 

The cheapest SATA card working out-of-the-box with Snow Leopard is this one (port-multiplier-ready):
http://www.span.com/product_info.php?products_id=16361&source=gbaseus&currency=USD
...or any other with the JMB362 chipset by JMicron (native support). This is, however, the only one I found for the US. You could also use a PCI slot bracket adapter to get the second connector out.
However, I bought a single-port JMB362 card for my 2006 Mac Pro and it didn't like the port multiplier I am using in my external storage solution.

So I'm saving for a HighPoint RocketRAID 2314 or RocketRAID 2302 (these are the cheapest) now because I don't want to juggle with port multipliers and hope that the HighPoint cards are really port multiplier ready, unlike the cheap card I have now.

And these RockeRAID cards are EFI32 ready; and I don't think that Apple would have incorporated the HighPoint drivers into Snow Leopard if they didn't really work properly.