Thanks for your answers Dark Blue Man and Ruffindajungle.
Yes, I’m comfortable with a screwdriver - repaired a lot of old PCs in my school and installed new ones a couple of years ago (I’m retired now).
I’ve been on PC from 1996 til 2008. I was not very lucky with a machine that was powerful (at that time) a dual-core with 2x MP from AMD. Precisely with the motherboard 
a Tyan …
At the end I build a 4800+ with an Asus mobo, I still use in my little music network but with only 3 gig ram recognized
because of the mobo. And as I wanted a machine with plenty of ram I looked towards Apple, got a Mac Pro and bought ram at OWC.
No problem to fix, only music to do…so I’m ready to buy a new one but if somebody tells me (s)he has a PC with say 32 gig of ram or more and overall Cubase 7 running faultlessly, I’ll consider building a machine again.
Are there people who manage to use many sound libraries (VSL,NI etc…) and VSTIs like Spectrasonics’ instruments and MachFive? If yes, on kind of machine?
Thanks in advance for your help.
Edmond