If you have room to consider alternative plans....
The "return through the manifold/upsize for the future" idea seems popular but I don't recommend it. Especially if your tank and sump are reasonably close together. Spec for what you have now, today.
For example:
A 150 Gallon tank needs anywhere from 300 GPH to 600 GPH for return flow.
At a "normal" six feet of head pressure, all it would take to do the job is a normal Quiet One 2200 at just over 300 GPH. At most a model 4000 to get you around 500 GPH. Either pump is about $50, only takes 40 or 50 watts, and comes with a 3 year warranty.
Instead of a manifold, simply use additional right-sized pumps for each application. Their models 800 and 1200 are only $15-20 and work well for most other applications since they are adjustable. Same warranty.
A Mag 7 or 9.5 would also do the trick at $90-115. Mag pumps have an even better warranty. Sicce and Eheim are other obvious choices in a similar price category.
I like one of the Quiet Ones myself.
These setups won't require any special plumbing or drains...1" will be fine across the board.
Use this friction loss calculator like this if you want to see how much head pressure your plumbing and fittings affect your design:
http://www.freecalc.com/fric.htm
Add the calculator's result to your base head pressure.....then use a flow chart to predict flow.
For a plain, ordinary return that's not really a required step.
