78 Gallon Cube - How Much Flow

[Josh23]

Im in the process of planning a new tank, been away from reef keeping for a few years and would like some feedback prior to making any purchases.

The tank is 78 gallon (30x30x20=78 gallons)

As of right now here is my proposed equipment list:

-250 watt PFO MH, 20 K bulb, Reefluxse reflector
-Sequence Barracuda close loop pump (4500 gph)
-Ocrean motion 4 way
-Closed loop returns to be located on the bottom in each corner

Undecided Equipment
-sump return pump (500 gph)
-skimmer

Total GPH= 5000
64 times tank turnover per hour

Proposed Fish:
-firefish x2
-yellow tang
-chromis x6
-clowns x2

Maybe:
-hippo tang
-pygmy angel

What are your thoughts on these fish - will they be effected by my proposed flow? I want to see my fish not have them hide.

As for coral....

SOFTIES:
-Zoas
-GSP

LPS:
-Hammer
-Flog spawn
-Bubble Coral
-Brain
-Candy Cane
-Shelve leathers

SPS:
-undecided but only a few.

Please provide feedback on equipment and gph based on stock list.
I'm also looking for skimmer suggestions.
Should I go with a BB or sand bottom?

thanks