I just moved into my basement in a tent as well so i feel ya man. Luckly it's in a room in the basement though so it's a little easier than it being in a large space. I actually have upgraded from a 250w being too hot in my previous closet to a 400w which is still not enough heat so 600w is coming on monday. So yeah i'm going with a bigger light to help warm things up. I also slowed my ventilation fan speed down to slow the exchanging of air so that the warm air created from the light stays a hair longer. I also am having to run a small heater where i set it at 65 degree temp, my exhaust blows near the heater so in turn my heater actually keeps my tent 70 degrees with light on, while the room itself is 60 degrees. When lights are out the tent temp drops to 60, which preferably i'd want it at 65 but I don't really have a choice. Temps will be rising soon in my area though so that should help. Ideally i want to find a bigger more efficient heater for next winter.
Normally basement temps without heater is 45-50 degrees.