advice before buying a thermostat

[Brently]

I am looking for some advice before I buy my thermostat. I have my eye on the spyder robotics herpstat II. I am finishing making an 8ftLx3ftHx2 1/2ftD wooden enclosure. I plan on buying a 160 watt RHP to mount on one end. I am curious if I will need both probes of the herpstat II? I am not sure if on the other end of the enclosure if I will need a heat mat or some sort of belly heat to keep a thermal gradient. I have never had an enclosure this size before. I keep the house around 75 in the summer and probably around 70 in the winter.

Will the RHP be able to appropriately heat that area or will I need supplemental heat on the cool side to keep it in range?