Intake, intake, intake...you say there is no hole in the front for an intake fan, so cut one! Use a dremel for the open air do the measurements (twice), use a drill for the screws. Aside from that, you could also add a side fan that blow directly onto your gpu. This would require cutting into the side panel of your case and adding a fan there.
If you don't feel the desire to cut, then I would suggest a new case before you start overclocking. Check out <A HREF="http://www.newegg.com" target="_new">newegg</A> and look at the cheiftech cases there.
Disclaimer: Please use all the appropriate safety equipment when attempting this, and make sure you take you computer OUT of the case before cutting.