I agree that if you are dead set on getting clowns that two of those fish is all a 15 gal
can handle and even that will be pushing it IMO
I'd also look at Live Aquaria's nano fish section
if you decide you want something other then clowns. You could keep 3 small skinny fish versus two stocky clowns which might be worth considering since the bio-load would be very similar.
Main concern is being able to maintain appropriate water parameters without large pwc
and also not having too many fish suck up the available oxygen if you have a power outage.
Once you do a fishless cycle
you can add 1-2 small fish to start and possibly 1 more after a couple of weeks depending on the type you choose.
I wouldn't add more then 2-4 hermits/snails to start with. Up to 6-8 hermits/snails once your tank matures more.