My third gauge would be Oil Pressure. You might also want to look into the Defi Link Display, you can have multiple aspects of monitoring with this system. All you have to buy is the individual sensors for the things that you want to monitor. I have a Spec.B so I dont have the cubby but I'm pretty sure that the Defi Link Display will fit in there.
http://www.defi-shop.com/product/dp/dp_top.html