XPS 15 touch HDD upgrade

Hi,

I got an XPS15 i7 QHD 16gbRAM with 32gb mSATA + 1TB HDD then I've upgraded the main disk to a SSD 512GB (Samsung 840 Pro).

I was surprised to see the Windows Experience Index showing the disk performance at 5.9 only. Is there any issue with the 2 SSDs (32gb + 512gb) configuration? I'm using Win 8.1.

Thanks