From my experience, the Ultratherm pads run cooler than the THG heat tape. I have both and use them for different applications. On my T8, I have both THG heat tape underneath and radiant heat panels (one on either side as mine is divided).

I also don't run heat in my room with the T8 and it sometimes gets down into the 50s. I have two 40 watt RHPs that have to do a lot of work to keep it warm, but they do maintain temps quite well. Only problem is I have to turn the heat tape down in the winter because when the RHPs run at higher power, they overheat the floor where the heat tape is (even though the heat tape thermostat reads much lower (since it is sandwiched in between the tape and the bottom of the cage where AP routes the channel for it). I haven't gotten around to it, but I plan on removing the heat tape and offsetting my RHPs so that they provide a temp gradient and just using them. They are currently centered on each side, but if I move both towards the middle, they can be set for my hot side temp and the cooler side should just fall into place with the ambient air.

I haven't tried it myself to confirm, but as was recommended to me by Pro Products, for a cold room and a full T8, I would get an 80 watt panel and mount it on your hot side, then get a Herpstat and set it the panel to your hot side temp. If you are planning on getting more cages or expanding your collection, you may want to think about a Herpstat 4 (or even 6 now!).

Hope this helps!