This is one of those cases where I'll urge you to stay your hand. Even power consumption won't improve in a jump to Haswell if you're trying to overclock, and IPC improvements between the two aren't dramatic enough to make up the considerable expenditure you'd make. Resist the urge to upgrade because you feel antsy. The 4+ GHz 2500k and second Radeon will serve you as well as anything. While the hyperthreading inherent to i7 chips is a nice feature for some edge scenarios, very few modern games will take advantage of it in a meaningful way. Unless something breaks, don't try to fix your current setup. It's not like it was in the old days when waiting a few years was like jumping from a Pentium to a Pentium III, or even an Athlon XP to an Athlon 64.
edit: Uh, your display will OC to 100 Hz? I think you just mean that it will support a high refresh rate...
Workhorse: FX-8320, 24 gigs RAM, Radeon 7970, Xubuntu 16.04 x64
Plaything: i5 6600K, 16 gigs RAM, Geforce GTX 970, Windows 10 x64
HTPC: i3 4170, 8 gigs RAM, Radeon R7 370, Windows 8.1 x64