Question about SATA add-on cards: do 4x PCI-E cards work OK on a 1x motherboard like the P5W DH?

I've been using a cheap 2-port RAID card in JOBD mode attached to one drive and it works OK, but now that I need more reliable connectivity I'm looking at an Adaptec 1405 with 4 SATA cables attached to its one SAS port. Trick is, it's a 4x PCI-E card so I'm not sure it's the BEST card to get. I also have an open PCI slot in case the throughput on that bus ends up better...