I would opt for whichever will provide you options for chilling the tank. If you go topless with the Viper, and you have high temperatures in your home, you will probably not even be able to run the lamp. Plan ahead, incorporate a chiller now. I don't know if the chiller they offer is good or not, but you need to figure what the highest temperature of your ambient room air is during the day, then choose a chiller that will bring your tank down from that temperature to 80 degrees.
Good luck,
-A