7990 in my system

Intel i5 4690k! Cooler master Seidon 120v, Asus Z87-K, 8 GB Crucial Ballistix
1600Mhz RAM, Sapphire 7970 3gb GDDR5, 120GB Kingston SSD, 500GB Seagate
Barracuda, Corsair Carbide Spec-01, Antec True Power 650 80+ Gold, NZXT Sentry
2 Fan Controller. EVGA 500 Plus PSU NZXT Sentry 2 Fan Controller with arctic
fans

So that is currently my system however I would like to replace the 7970 with a 7990 as the performance difference is very great, however I was wondering if my system would power this as I know the tdp is 375 however it will draw more than that, probably 450w so I was wondering if my PSU will be able to support all of this?

You'd need a new PSU for sure.
Also, the performance difference is only large in applications that take advantage of CrossFireX.

You'd be better off upgrading to something like a 290 or 970