Best HOB for my 20Long?

Hello everyone! I'm setting up my second saltwater tank, a 20 long FOWLR. I may consider Coral in the long run. I would like to know your opinions on what the best / most appropriate HOB filter would be. I'm anticipating having to modify an intake to work with the shallow depth, or DIYing a spray bar if needed. Both of which I don't mind doing. There is a King-225 Powerhead in the tank along with 15-20lbs of cured rock. Substrate is a mix of Black Diamond blasting grit and pool filter sand. There are also two large sponge filters in the tank powered by a Tetra Whisper Air 100 (I was using the tank to breed ghost shrimp.) I have not settled on livestock at this time. The placement of the tank is not conducive to a sump or canister filter, nor do I wish to peruse these options. Thank you all for your time and help!