advise on what heatmat to get

I have this setup Vivexotic vivarium LX36 915 x 375 x 405mm 36 x 14.8 x 15.9 inches (L x D x H) from 888reptiles (complete Leo setup) but it didn't include a heatmat?

Was hoping someone might be willing to advise me on the best wats and size heatmat for a viv of this size

ULTRATHERM all day long

This is the one I would get if I had a viv that measured 36x14x15. http://beanfarm.com/product_info.php?cPath=1204_1206&products_id=5579

http://www.reptilebasics.com/ultratherm-undertank-heater-uth-11-x17

Hope that helps. Just so you know their temperature range mentioned in the write ups is a bit off. With out a rheostat I've seen my T-Rex cobra heat mat get up to 106*F. They are designed to operate at a steady 100*F. I can't find my original sites I had book marked that gave a much better description as finding accurate info on google about them is difficult. Sorry.

You can read more about my opinion/where to buy, ultratherm and T-Rex Cobra heat mats here: http://www.leopardgeckoforum.com/t2805-where-to-buy-ultratherm-t-rex-cobra-uth