Welcome to the Boards!
And welcome to the wonderful world of saltwater aquaria. BEFORE you jump into setting up a saltwater aquarium, I urge you to check out all of the stickied threads in the New Hobbyist section to read about equipment, cycling and fishes. It sounds like you have done some research, and you have come here, which are all great steps to take for the health of your aquarium. Freshwater is a whole different animal than saltwater, and saltwater aquaria has different procedures and a lot of fun and interesting equipment that is necessary to keep your fishes happy.
Do not use silica sand. Silica causes massive diatom blooms - this brown algae- and will be an eyesore for the entire life of your aquarium. The only play sand that you could use would be Southdown white sand, but the company I think went out of business and it's very, very hard to find it. If you do, buy me a few hundred pounds and we'll call it even
. You do not have to get live sand at all. Most people on this site start with Aragonite sand, oolite or semi-course sand is perfect. Live sand is too expensive for the small amount of benefit that you can get from it. A sand bed of 4-6" is absolutely not needed unless you really want a deep sand bed. If you did, I'de go closer to 6 than 4. A sand bed of 1 1/2 to 2" is perfect. However, if you have a deep sand bed, there are some critters that you will need to buy to keep it well turned over.
The skimmer that you have your eye on looks pretty good, and it is a good brand. I think you will be very happy with it. It's good to know that you are not going to go with a Seaclone 100 skimmer, which is a newbie mistake a lot of people make. A skimmer, however, does not replace a filter. In a heavily stocked fish only with live lock (FOWLR) aquarium, I highly recommend getting a hang on back filter such as an Emperor 280, for your size tank. It will allow you to run two filters at the same time, so you can change one filter out and leave the other one in to prevent sudden changes in water quality and filtration capacity. Others have had success with canister filters, however I don't like them because they require a lot of maintenance.
Your stock list is pretty good. Most people go with a six line wrasse for their first wrasse. I don't know much about carpenter wrasse, so I don't have any advice there. Maybe some others can chime in.