johnners2981
Honestly, I don't think anyone with an i7-9xx should rebuild any within the next 18 months.
The reason is because I look at things from a practical stand-point; what is the bottleneck of my system right now. At the resolution I play (1920x1080) the bottleneck is definitely the GPU sub-system. How do I know? When I overclock my GPUs, there is a direct correlation with how smoothly things run, but when I raise/lower my CPU overclock, I don't notice a difference (3.2~4.0 GHz). When my GPU speeds no longer makes a difference, that's when I know that I've hit a system wide dead end.
I built a computer in 2001 with an Athlon Thunderbird and used it quite well until 2005 with just upgrading the RAM and GPU. I built another in 2005 that ran until it died until 2007, again only upgrading the GPU. I had another that went from 2007 till 2009 with no changes. My system was always GPU limited, and even with 5850 in crossfire that is the case. The 4.0 GHz OC I'm running right now is mainly so that some of my older single/dual threaded games run faster (namely Civ IV).
Yes the Sandy Bridge is faster/better/whatever, but personally I'm going to wait until my system actually struggles with games. Even when beating it as hard as I can in Star Trek Online or Bad Company 2, my GPU subsystem takes the beatdown while the CPU is working at a nominal level. Even when I was not overclocking, my GPU was still receiving the main workout.
My opinion would be to keep your system, upgrade graphics every year or two, and buy a new/more monitor(s), upgrade your sound system, whatever. Maybe when Ivy Bridge or even Haswell comes out then I might consider an upgrade.