The 'modern' saltwater tank is very natural with live rock being about 80% of your filtration, with a skimmer and fuge making up the rest. With fish only I wouldn't worry about the fuge.
In most cases the live rock you get will not be cured, or at least won't be by the time you get it home. You wil have to setup a different tank to cure it in or KNOW it is cured and transport it home completely submerged in buckets and hope nothing goes wrong.
Your rock is a great start, but I would get some high quality live rock to go on top of it. This will seed the rest, which will eventually become live rock.
Out of all the tanks I have maintained or helped customers with the ones that crashed almost never had a skimmer running.
Most saltwater people don't use canisters or trickle filters because they tend to trap a lot of debris which breaks down into nitrate and phosphate. If you make sure to clean the canister very well EVERY MONTH that should not be a problem. If the tricle filter uses bioballs take them out and replace them with rock rubble or nothing.
What lighting do you currently have? Most likely I wouldn't worry about converting to LEDs. I have not really seen any LED
tanks that made me want to switch. HOT5s with individual curved reflectors are the way to go, unless you have a reef tank over 24" deep in which case you want the T5s to supplement your halides.
Max fish is what gets along and you can keep the nitrate down on. This may not be much more than the pair of clowns, but it might be a lot more. Almost every tank should have a blenny, goby, wrasse, and a few others. It is your tank, see what you like, make sure it is compatible, and then try it out.
Plan on going reef. Unless you only like fish that are completely not safe for a reef and have a huge tank for them (not you), most likely you will want to go reef at some point. The last thing you will want to do is make major (expensive) changes to your tank or tear the whole thing out to get one little fish out.