Server question

Thanks for looking, I have a Dell poweredge server 1300 dual 500 Mhz PIII slots, 768 Mb of Ram. It works perfectly 24 hours a day, so what do I want to do? I wanna mess with it.
My plan is to swap out the two 500's for 1000's, bring the ram to 1 gb, and now for the question.
I currently have 1 30 gb drive with the OS, and a few other programs, and a standard raid 0 setup with striping over 4 20's for 80gb (74.4) This is through a ide raid card. I want to bring it up to half a tb, with room for expansion later so I'm going with 2 250 gb drives. so far so good, my question is:
Will I notice a difference if I go with sata II through a PCI sata card. For faster data transfers? Also with my os drive running on IDE am I creating a bottle neck, if I put a sata drive in would that greatly improve performance.

Thanks in advance.

 

Bump- Anyone have any input ?