Thanks for the thorough response!!
I've yet to gather any supplies for my project, so can't give you exact measurements on my skimmer chamber. I'm planning on getting the sump kit from Modular Marine for a 20 long. I plan to make the sump chamber dimensions match whatever skimmer I end up getting. I definitely want an in sump skimmer versus an external one.
Budget wise I would like to stay at $200 or under. With that said, I'm planning on making this system the best I possibly can. So I have no issues waiting on funds, if needed, to get what I need/want. I'm not rushing this process by any means.
Noise is also another consideration. My setup will be in the living room next to the TV. So something that's going to be even remotely noisy isn't going to fly.
Thanks again!! Never would've considered things like going with one that can handle a heavy bioload of a tank twice the size. Makes total sense now though.