Could I run 1 1TB WD Green and 3 750GB WD Green with the 1 TB partitioned to 1 250GB part for OS and the other 750GB being implemented with the other 3 750GB WD Greens creating a 2.25TB RAID 5 array? Would I need Intel Matrix to do this or could any current MB handle it?
You can use Just A Bunch Of Disks or JBOD if your motherboard allows it.
Or you can do RAID5, by using only 750 GB of the 1 TB disk.
Or you can do RAID5 with 3 750 GB disks and use the 1 TB as a single disk.