I have to admit, I'm surprised that the temperature would drop that much just by cleaning out the dust. You must have had a lot. But regardless, I'm glad to see that things have improved quite a bit. As long as this keeps up, you shouldn't have to worry about fixing/replacing anything, which is a major plus. To be honest, I didn't have high hopes, but after seeing your new results, I think this should work out. Your temperatures aren't perfect, but they're certainly better.
If I were you, I would still consider getting a cooling pad, as long as you can find one that's fairly cheap. You don't need anything fancy. And I wouldn't worry too much about the power. They don't use much power at all (there might even be some that are battery-operated), and the little bit of extra PSU usage shouldn't cause an increase in temperatures. Personally, I think it would be a good investment, but maybe that's just me.