If you are looking for a 4-port SATA card with PCI interface for under $60 that works with WHS, try the
SIIG SC-SA4011-S2 PCI SATA Controller card. No extra drivers necessary, WHS grabs the latest ones online. I installed it after I already had the system up and running.
Dell SC420
2.53Ghz Celeron
1 GB RAM
Onboard SATA controller - 250GB HDD
SIIG SATA controller - 2 x 500GB HDD
It runs great and leaves you room to add on more drives in the future. Got mine at newegg and I highly recommend it.