What is the best RAID for me? 4 SATAs and ICH9R Intel

Hi

I have Intel P35 ICH9R MSI motherboard, I have RAID0 with 2 disks and RAID1 with 2 disks. Each disk in a pair identical to another but pairs are bit different in size. All are Seagates Barracuda (roughly 2 x 320 and 2 x 250Gb).

I used to have Vista on RAID1 and Win7 on RAID0. However after the Win7 release now I am not going to use Vista ever... I am looking for simple and easy way to squeeze more juice from those 4 disks.

I dont need much of space but I'd like to have speed and redundancy. Also I would like to find a less painful migration process. The OS must be intact during the migration.

What would be your solution in a such case?

Is it possible to migrate RAID0 into RAID0+1 or RAID1+0 or RAID1 (as worse case scenario) not having OS reinstalled?

Thank you

anyone?