I am interested in getting into the Scope universe, and I would like to be clear on some things, and I hope you can help

People talk around about 6 dsp, 10 dsp, 18 dsp systems etc.
As far as I know, there are 1st, 2nd, and 3rd generation DSP sharc hardwares (PCI cards or Xite-1). Some say the Xite is more powerful.
Does a 18 DSP system have the same processing power, whether it comes from a bunch of PCI cards (Luna, Pulsar, Scope Pro etc.) or a Xite-1? If there is a difference, what is the approximate ratio in terms of processing power between DSP generations? What are their basic differences?
What is the approximate lifespan of a PCI card? I know some have been around for 15 years, but can they survive 20 years of use?
Regarding the Scope Software system:
A) are plugins attached to a PCI card or to the user? Can they be transfered from one card/user to another card/user?
B) If you buy a Sonic Core or 3rd party plugin for Scope V4, what is the fee you have to pay Sonic Core to use that plugin in Scope V5? is the fee per plugin, or one fee for all plugins you may have from previous Scope versions?
I appreciate your help.
Thank you,