Computer Requirements for Music Composition

Got a friend/client that needs a new computer for music composition, but I've never dealt with this kind of computer builds.

His current system is an old Q6600, 8Gigs of RAM and he tells me that he is hitting the limits of that rig while running all his software.

His current software-hardware setup is as follows:
CPU: Q6600 (stock) on P35 motherboard
RAM: 8Gigs DDR2 1066MHz
Audio Hardware: TASCAM FW1884, Roland RP101 Electric Piano, Yamaha Studio Monitors
Software: Cubase 5, a ton of plugins, a ton of VSTs, and a giga-ton of samples (Kontakt 5) (that's how it got described to me)

He invited me to his home studio to listen and observe how the system can't handle his compositions any more. While on stand-by (not playing the composition) the CPU constantly sits at around 40% utilization, and while playing it hits 98-100% constantly on all cores. I didn't notice huge RAM consumption tho, around 70%.

I guess @Logan could pitch in, since he is also a music composer. I searched around for the software min-specs and saw that Cubase 5 is really old, but I guess when he got the computer Cubase was ok on the system and probably still is. From what I understand, the plugins, VSTs, and Samplers consume all the performance from this old system.

What does this software require? CPU Power or massive amounts of RAM?

Would an i7-6700 with 32Gigs of ram handle anything that he can throw at it? Does music production require ECC memory and workstation grade hardware?