Oh Wow, I know exactly what you are going through. I received a 75 gal tank for Christmas and have been 'setting it up' ever since.
Are you going fish only or reef? It makes a difference.
I used very fine sand-6 bags of it for my substrate, filled it with distilled water and salt to get the Specific gravity right. Added two Aqua clear 900 power heads with filter cartridges for aeration, then went searching for the right wet/dry
Well, that was an experience-trying to match overflow, sump size, return pump etc.
ended up with the Marineland Sump and their SOS overflow. using a magnum 7 for my return. I have a Euro Reef skimmer in the sump. Took out the bio-wheel on the marineland and run it with just the skimmer and power heads.
Then I added about 50 pounds of base rock to the tank and another 50 or so Figi live rock (which is the only kind they sell at my local fish store)
I purchased the Orbit Power Compact lighting system-because I like the price and the look. It comes with daylight/actinc and lunar lights all in one nice unit.
Let all this run for few days-check your ph and salinity-You will need to purchase a good test kid for your Ammonia, Nitrite, Nitrate, Ph-minimal.
Oh, forgot the heaters-submersible-two 150's, one at each end of the tank. You could use one, but two gives you a back up if one ever goes out. Cant remember the brand, but dont skimp-get the best one you can.
You might want to purch some of the new biological 'starter' stuff from your fish store to get things going. My tank cycled incredibly fast-within two weeks everything was doing great, live rock purpling up, a few snails showing their heads etc.
So far, I have added 3 cardinal fish, a brittle star, 10 turbograzer snails, 5 peppermint shrimp and some mushroom polyps. Have done two 20 gal. water changes to make sure Nitrates stay low.
Be patient-buy the best quality you can afford-you wont regret it. and enjoy your tank!
Granny