Looking for advice ( new build )

Dear community,

I've been using unraid for around 4 years now, mainly as a NAS.
I used some old stuff i had.
AMD TR1900X, 16gb ram, 4x 1tb hdd, 1 x 2tb for parity, 2x 480gb for cache and a 110gb ssd to test outside of the array.
Recently i added a RTX2060 because my interest in running VM's with GPU Passthrough ( too bad i haven't got this working yet, i think because it's the only GPU in my system )

Now that i am more interested in running more on the unraid build, i want to upgrade my hardware, but i don't want to have any problems running GPU passthrough.

To follow the new build guidelines, hereby the answers
 

What is your budget?
€3-5k

How many drives do you want your server to be able to support and how much capacity do you need?
2x 1tb M2 for cache
4x4tb for the array
2x6tb for parity
1x14tb for outside of the array ( unimportant files )
 

Is expandability important to you?  If so, what's your long term goal?
Not really, as above list of drives covers all my needs
 

Are you interested in running additional apps?  If so, which ones?  Be specific.
Just unraid with some dockers,app and 2 VM's
 

Do you want to run green/low power drives or faster 7200 rpm drives? 
faster drives
 

What do you plan to run for hard drives?
WD red plus/pro
 

Do you have any spare parts laying around that you would like to apply towards your build?  
Yes, but i focus on a 100% new build, i would like to add the RTX2060 as GPU for VM as i just bought it last week.
 

Now i wonder, do i need to add a second GPU so that GPU passthrough works easier?

Thanks in advance, 

Erwin