Finally got my new W10 system build
So am I right by saying I firstly have to install X3 to get Pentagon and X2 to get V-Vocal
Seeing neither of these are included with Splat?

I believe you can install those plug-ins after the Splat install. You set up to install X2 & X3, but choose the advanced install option, which allows you to just install the only the plug-ins that you want.

Run a minimal install of X2 and add the other missing plug-ins such as R-Mix and Pentagon in the selection screen. Pretty sure everything you need is available in X2. There is no need to install of X3 unless you want to do so.
 
Here is a similar thread http://forum.cakewalk.com/FindPost/3611714 but in this case the most recent version the user had was X3.
 
Installation order should not matter but I always install oldest first if possible.

Thanks :)
Yup X2 will give me  R-Mix, Pentagon and Vintage channel. 
Would it be wise to install X2 before CC to load slpat
What about ProChannel PC4K U-Type Bus Compressor and ProChannel Gloss EQ ? suppose I'll have to do same with X1

When CCC is installed does not matter at all. There are a few things in X1, read the thread I linked in it there is a link to another thread with a plug-in breakdown by version. All the PC modules bundled with X1 Producer through X3 Producer are included with Platinum.

Anonymungus!
I believe you can install those plug-ins after the Splat install. 

Thanks.
make scene, will load splat and pick the eyes out of X1, X2 and also from memory there are some Dim-Pro samples that came with 8.5.3 that I would like to retrieve.

Will do and thanks scook for your explanation 
 

While installation order should not matter, unless there is some compelling reason, I would recommend running the X2 minimal install first. The rest of the advanced installs do not matter because they will not involve installing the SONAR core.