No, it isn't worth upgrading to the i7 930 when you already have the i7 920 CO or DO. I would recommend upgrading your cooler or revisit your HSF application to improve the cooling to improve upon your cooling. Either version of the i7 920 can hit 4 Ghz on air with the proper cooling, which is much cheaper than a new CPU.
89C on the cores...
So that's like 85C "CPU Temp" (Tcase), which is a tad over Intel's spec of 67.5!
I know most of the time you wouldn't be loaded like it does in prime95, but I'd be wanting better cooling than that.