System drive on PCI-X controler card? Can i do this?

Help me out with this;

Q: Can I a new Raptor 150g system drive on A PCI-X SATA-II controller card that i also use for hooking up eSATA disks to? My motherboards Sata controllers are all full with a 4 disk RAID Array.

As of now, my system drive takes way to long to boot windows and to restart takes like 3 solid minutes, and My system drive is an old IDE 250g Wester digital from 2003. Which means its getting old and could go out any day now so needs to be replaced. The system around it is fairly new and high performance all around.

I want to get a Raptor 150 drive to replace system drive. After seeing a colleges computer boot windows and programs so much faster i realize i must have one. Im wasting productivity to do otherwise. However, I am out of SATAII ports on my motherboard (There all used for a 4 disk RAID) (i do uncompressed video editing)

So what are my options to have a RAPTOR system drive?
Could i buy some kind of PCI-X hard drive controller card and put my system drive on it? I realize the correct config would be system drive on motherboard controller and RAID array on PCI-X SATAII controller card. But that is the more expensive configuration.