You always want more GPH in your overflow than your pump can do, if it's then less or just at the pumps speed, you risk the tank overflowing.
Stuff I needed:
Pump A mag-drive is fine.
Overflow I listed two earlier, check those out, I use the big one.
Powerhead - I use one from marineland, I think it's called a penguin, I also snagged a reverse flow kit (has an intake sponge.) Ususaly stronger powerheads have a stronger venturi effect, which will pull air out of the overflow faster (good thing.)
Egg crate from a hardware lighting department.
Pot scrubbers from a dollar store for bio media
Polyester floss (No flame retardant or tactifyers) for mech filtration
Airline tubing
A semi fine grid to keep fish out of the overflow and returns (lost two loaches till I hacked up a XP3's shelving grid to stop them.
If your pump is going to be external, put a towel under it, if it's submersed use a sponge made for aquarium filters to stop the vibration.
TONS of PVC.
Also, look into making a Durso standpipe or Aquasilencer (also called a stockman standpipe.)
Two unions, 3 ball valves, tones of 90 degree's, couple 45's, some T fittings, a couple caps, half dozen reducing bushings, a bulkhead or 5.
Get the next biggest size in unions and ball valves, prevents a bottle neck.
You can always return stuff, look to make about 10 trips to the HW store as ya go along.
My pump outputs at 3/4ths, I upsized it to 1.25 inch PVC to reduce friction.
I also took the returns and joined those into a single 1.25 inch pipe to save some hassle, and my pump isn't strong enough to require two 1" pipes.
If you're making your own sump and baffles for the custom aquarium, check out this site.
http://www.wetwebmedia.com/ca/volume_3/cav3i1/Baffles/baffles.htm