To get the equivalent between incandescent and halogen, multiply the halogen wattage by 1.15. Thus your three 20w halogens adding up to 60w will be the equivalent of a 69w incandescent. For that space, they should be bright enough. The next up halogens at 40w each, you might need sunglasses!
It's a matter of taste. As it is such a small room you may be ok, but I think I'd prefer a forth light somewhere. Maybe 'suck it and see'. When I did my kitchen I thought 6 would be enough, once they were installed I thought them too dim. But one gets used to them and they seem adequate now. Not really as bright as a kitchen should be, but okish.
Thanks, OG. I have downlighters in my kitchen but have not checked their power. With six of them it's bright enough - don't want it to show up the grime!
For safety from the heat point of view and economy I'd recommend replacing halogen with LED lamps.
We have 3 x 4 watt LEDs in a bathroom of the same size and it's fine.
They're expensive to buy but very cheap to run.