Zachy - please, you now have about 4 or 5 different "ideas" for tanks, all of which you're talking about horribly overstocking. I am not trying to be a jerk here, but as someone who seems very new to the hobby, you want to UNDERSTOCK your tanks, at least initially. The more stuff you cram in there, the more likely you are to have water quality issues, breakouts of disease, internal strife between livestock...even peace loving fishies can get pretty pissed at one another when they have no personal space.
Lets do the math.
Maroons can get to be up to 6" each. That makes 12" of fish right there. Add to that the fact that, unless they're a mated pair, in a 40 gallon tank what you'll get to watch is the two of them kicking the crap out of one another. If you do a bit of homework, even just reading up on liveaquaria it says they will be aggressive towards other clownfish and are difficult to maintain together:
Saltwater Aquarium Fish for Marine Aquariums: Yellowstripe Maroon Clownfish
Lemonpeel angel - also gets up to around 6" and is considered semi-aggressive. So you've now already got 18" of fish, all of it semi-aggressive. That's nearly half your bioload already if you are absolutely maxing this bad-boy out...and that's not taking into account the plethora of space taken up by either liverock or decorative rock for hiding spaces.
Dottyback - better choice for a tank of this size. They stay much smaller and, while semi aggressive, generally only acts out against other members of similar species - again, assuming you are providing a ton of places to hide.
Butterfly fish - they're all big...even the most common, the yell threaded I think its called, gets to be around 8".
Adding one other semi aggressive to the mix above in the size mentioned is roughly akin to dropping 30 convicted mass murderers into a hole and then airdropping knives in. That many semi aggressive fish in that small a space, what you're going to end up with is a fish version of pit fighter.
Now, if I had a 40 gallon tank, and I were stocking from scratch, I'd probably go with something like this:
ocellaris clown (Stays smaller then the maroons, still very hardy...but can be somewhat aggressive)...or if you're not doing reef, maybe a clown goby: they're really pretty, stay around 2", and are a peaceful fish: perfect for a smaller tank.
Firefish - again, peaceful, stays around 2 - 3" etc...you could even add 2 if you wanted
2 - 3 neon gobys, again 2" a pop.
The above gives a bioload of around 10" - 12" of fish, which your tank should easily be able to handle...and it'll leave some room for adding additional small fish or crustaceans later once you have a good handle on things.
Something that you need to keep in mind: inch per gallon is a guideline not a rule...and when you're talking about semi-aggressive to aggressive fish, that percentage goes way, way, WAY the **** down. Thats why people who want to maximize the number of fish they can cram in generally tend towards smaller, peaceful fish.
So yes, going by numbers your list should fit into your tank. Going by experience it's a recipe for disasterous water conditions and angry fish all around.
Keep in mind you can always add MORE later - but its usually difficult to remove fish before it's too late. Start conservative, it'll save you a ton of cash and heartache in the long run. The other option that'll help to satisfy you, in light of the proposed fishes you want to use, is to hold off and buy a larger tank when you're able to do so. While I'm the exact opposite of you (meaning that I massively UNDERSTOCK my tanks), I would say that the list you gave here would be more appropriate in a tank around 60 gallons...but again, I'm ultra conservative about such things. To give you an idea, my 72 gallon tank (before being wiped out) had an ocellaris, a foxface, a pajama cardinal, a blue chromis, and a sleeper goby. That was it. All relatively small, peaceful fish...on top of a butt-ton of liverock for hiding spots, and with a few ornamental type shrimps thrown in to keep the tank interesting. I've always dreamed of having the kind of tank where I could have herds of yellow tangs swimming around...but until I have the space for that 500 gallon dream tank, I try to keep myself realistic about what I can and cannot do.
If you REALLY want to cram a lot of pretty fish into a small tank, look into african cichlids. They're gorgeous, are used to fairly murky water conditions, and are used to being crammed on top of one another. I had a 36 bow with around 8 of them in it...a tank which I ignored horribly in terms of maintenance, went the chemical route in terms of algae and disease control...and those fish flat out could not and would not die. They remained beautiful and healthy until I broke the tank down and traded in the fish towards saltwater stuff.
