Try the following but be carefull:
Go to Task Manager / Processes / when cubase is runnung what is the average Kernel Value under ( memory ) ? Right click on cubase / go to set priority / What does it say ? set to high ! and also right click and check "sett affinity to : all prosessors and make sure all 8 is ticked.
You have a powerfull system (as mine) although I have much more RAM
Make a new dummy project open for this:
Do the following test. take a project with say 10 tracks ( stereo audio ) and dublicate them a few times to get say 80 to 100 tracks, then go to pool and convert them to say 96 khz and 32 bit float > check now if your kernel value goes up while cubase is converting ?