MSATA & UEFI - XPS 8700

Is there any way to make an MSATA on the XPS 8700 the boot drive when utilizing UEFI?

Configuration:  XPS 8700, 8GB RAM, MSATA added, 2 HDD added (total of 3 with original HDD present), Win8

I ask because, after adding two HDD and an MSATA if I default to UEFI I boot from the original HDD (from factory) but can see all my HDD as well as the MSATA...I just can't boot from the MSATA.

If I default to Legacy I boot from the MSATA (much faster!) but can't see one of my HDDs entirely...and there's plenty of data on that disk that I want/need.

Advice anyone?