Why not RAID 1 ?

I have 4 HDs on my PC, 2 * 1TB as RAID1, and 2 * 1.5TB as RAID1. (I also have a 240GB RevoDrive SSD as my C drive)

The 1.5TB HDs I get really good transfer rates, up to 120MB/Sec (if I remember correctly, I'm not home right now to double check)

Windows Experience just gives you a score, use ATTO Disk Benchmark, it gives you the actual transfer rates...