Without making any mods to the case, fan, heatsink or anything else in your system, you will probably still be able to get close to 117 MHz X 5.5 = 643 MHz.
If you add 1 or 2 high volumn case fans, a good heatsink like an Alpha with fans on it, and maybe even a peltier sandwich cooler you will easily hit 124 MHz X 5.5 = 682 MHz and maybe even 133 MHz X 5.5 = 731 MHz. All of the above items can be added for about $100-$150 and some home grown installation.