IMO set it up with sand from your LFS. Just buy the bag, not the LS, just sand. Yes it will cost more then the lowes sand.
But once the tank is up and running- Do you want to regret that little bit of savings now that you have cyno/diat, etc.. overtaking your tank and you spend how much time and money getting it right.
Wait you get past that then start to add corals but they don't do well then start dying. Could it be the $20 you saved on sand?
I am saying this because I have been there. I left this hobby for those reasons. I was sure that I could buck the system and make my tank work by cutting just little corners.
Well, It does not work!!!!!!!!!
I have started back and doing everything the best that I can. So far so Good!