UX51VZ

Hi I have a 6 year old ASUS Zenbook UX51VZ (or U500VZ - not sure why it has two names). It was born with two 128 GB SSDs in RAID0 configuration. I would like to upgrade the two SSDs to two times 256 GB or maybe even two times 512 GB. However, it seems the installed drives are not standard...

I'm planning on getting a new motherboard/CPU and at the same time getting an SSD for my OS. I'm wondering if it is possible to keep all my games/misc. data on the HDD but removing the Windows from it. I still have my Windows 8.1 disc and key in hand so that won't be an issue. If there is a...