I don't think that my current two (going on three) tanks require alot of maintenance, and that's with weekly water changes, so I wouldn't worry about it adding too much maintenance time on top of your saltwater tank.
I'll let others that have angelfish comment, but I thought that you needed 55g or larger to keep angelfish. I could be wrong.
I don't think that any abrasive substrate would be a good idea in an acrylic tank. I have a 2.5g acrylic that I just started, and I used Fluval Stratum because it's a soft substrate that shouldn't scratch the tank. I recommend that you consider something similar. Actually, if it's not a small tank, I wouldn't even get an acrylic because they scratch so easily. Any reason you decided to get an acrylic tank over glass?
My tanks are all planted, and I don't have an elaborate CO2
system. I dose with Flourish Excel on a weekly basis to get the plants the carbon they need, and it seems to work fine for me. Then again, my largest tank is a 20g, so others might recommend that you go with a CO2
system rather than Excel.
I'm very glad you've decided to fishless cycle your tank. It will be worth it in the end.
Welcome to the other side of fish keeping!