DaveW, I have two Hydor ETH 300W inline heaters on my 150g setup and they keep temperature static at 77 deg F, regardless of room temperature. The room temperature can get as low as 40 deg F this time of year.
I highly recommend these heaters. But I would also install hose clamps for good measure.
Never used one but pfk gave them a good write up. They use ink heating technology witch hydor reckon is the future supposedly no more cooked fish when the heater breaks. On there old internal heaters is wasn't that reliable but they reckon the problems are sorted. There a lot cheaper than going for a ehiem thermo filter.
I wouldnt mind it so I could get some junk out of the tank. Hate things in the background.
As for extra hose clamps I dont see the need as the nut bites into the tube and squashes it into the thread. I have some stop valves on my tank with the same fittings and I find them fine.