Welcome! VERY good to see you starting out with a 60 gallon! Is this the similar to a 55 gallon long, or is this the type that is basically a tall 40 gallon breeder? I ask this because this can havea huge bearing on the type of lighting you end up using. It will be easy to become overwhelmed with some of the advice that I give and others give as well. Please be patient and hang in there, everything is recommended for a reason, many of us (including myself) wish that we had better guidance when we first started marine aquarium keeping, this is your chance to limit the money wasted on crappy or useless equipment, and focus your funds on a good starter set up. Much of the recommendations that I give will be as if you are trying to save as much money as possible upon initial start up. Make sure you also read the stickied threads at the top of the thread list which are there to help people like yourself start up a marine tank.
My first and highest recommendation is to get the tank drilled! If the tank is tempered on the bottom (good chance of this) then get the tank drilled with a hole that will accomodate nothing smaller than a 1 inch bulkhead fitting (fitting that enables you to connect piping to the tank to drain to a sump)
Some people decide to go with the siphon overflows to drain to a sump, but these are accidents waiting to happen. I recommend getting the tank drilled first and foremost, this should only cost you about $40 to have a local pet store or glass shop do for you, or if you happen to find someone in a local marine aquarium club that may do it, then you might be able to have it done for cheap.
Coralife makes good needlwheel skimmers that are just about the most inexpensive of their type on the market, I would look into one of those, or if you want to spend a little more money for a better skimmer I would look into the ASM skimmers (I love mine)
Titanium heaters are great, I would get two small ones, in your case I would get two 150 watt titanium heaters, this ensures that in the case of one of the thermostats sticking or not coming on, the other heater would either not come on, or stay on, which would keep the tank temp more stable in the case of such an emergency.
digital thermometer
Refractometer, much more accurate and unaffected by temperature swings like a hydrometer is.
Lighitng-you'll have to get back to us about the dimensions of your tank, then recommendations can be made.
Flow-again, get back to us with tank dimensions
sump pump-ehiem makes some of the best submersible pumps, they are very reliable as well.
I would go with a fine sand bed, this makes sure that waste doesn't have a place to sit in between large grains of crushed coral. You can always add a small amount of crushed coral for some variation int he substrate.
Maroon clowns do get pretty large, and would rule the tank when the become full grown, I would not recommend them in this size tank. The yellow tang is definitely not a good candidate for this small of a tank as well. But I have good news! There are MANY very cool fish to pick from that are just as beautiful and full of character like the maroons and the tang. I would suggest that you check out liveaquaria.com just to see what many different possibilities there are, and there are also tank size recommendations (usually pretty accurate)
I hope I got you off to a good start, don't forget to also check out that threads at the top that are for thos just starting marine tanks. Again, WELCOME!
