Not really..if you into benching your video cards then yes. I don't think overclocking your video card acheives a lot in real life use.
BTW if your CPU is aircooled then having your case fans running as fast (as you can live with
)..your internal case temp will have a detrimental effect (not life threatening lol) on your CPU cooling.
I overclock every CPU I get and for me heat is an enemy so keeping your case cool as you can is only good if your aircooling your CPU.