For orchestral stuff, having everything loaded in Vienna Ensemble Pro is the way to go, especially as those are not something you would be making changes to the patches.
I have HS, HB, HOW (all diamond), percussions from SO/SD loaded and ready to go in VEP all day (decoupled/preserve), so that I can open/switch Cubase sessions without reloading samples for every project. I am running VEP in the background on the same machine I run Cubase on. It saved me so much time.
It is possible to put just part of the libraries on SSD. I have a 250 GB SSD from Samsung, and I have only the main mics from HS, HB, and HOW on that disk - the rest is on another HD. I am using symbolic link to get the folders on the HD to point to the SSD.
Complete Guide to Symbolic Links (symlinks) on Windows or Linux
This can be done easily by using a utility called Junction Link Magic (must be run as administrator).
Junction Link Magic
As for Play 4.1.x having peaks - what engine level are you using? Having it set to Medium works well here. I am still on Cubase 6.07, though. 256 samples as buffer for RME HDSP9632.