Hi,
On a heater, rule of thumb is 5 watts per gallon. You can go less watts per gallon with Titanium though. If you have a really cold room, i would increase that, if you have a really warm room can decrease.
If you are not sure on brand, we feel the Ebo-Jager is the best quality glass heater you can get and the Finnex is the best quality Titanium heaters. We carry many other brands though, we just seem to favor those.
thanks