Um..more advice? I wish I could give you some, but you're asking for an awful lot of information in one setting. You do want a 75 gallon tank still? Do you want inverts or no inverts...what type of fish do you like? Let's break it down.
Filtration:
You said you wanted a sump. Well, that involves an awful lot things:
1) A drilled tank, those can be costly
2) A sump, most people use any old glass tank, although I've seen plastic sweater boxes do just as well. the volume size is up to you.
3) bioballs or some other sort of media. Do you want a wet/dry trickle or are you just going to run conventional filtration on the sump?
4) powerheads and calculating flow rates so you don't overflow your tank or your sump.
5) Plumbing, that could be large guage tubing or PVC pipes or lots of things
How to put it all together? Damned if I know, I'm not that technically inclined. Personally, I don't mind stuff hanging off the back of my tanks, and a good canopy can hide it (they have nice matching stand/canopy sets at my shop, one of them in beautiful cherrywood). If I had my own 75 gallon fish only marine aquarium I would set filtraton up thus:
UGF flitration with two reverse flow powerheads in the back corners, I forgot the brand name, Aqua something or other.
Two AquaClear 300's, one on each side for suspended macropartical pick up, boxes stuffed with angel hair (filter floss).
Two Fluval 203s, one on each side, sealed with bio-media
A Prizem Protien skimmer to run for a couple of hours each day.
Metal hylide lights are really only reccommended for coral reef tanks (the salt water equivalent of a thriving dutch style 120 gallon planted freshwater aquarium). If you are just doing fish, I wouldn't bother about metal hylides, they're costly enough as it is.
There is -so- much information, and so many different ways to do a marine aquarium, you have to pick what is best for your skill level and budget. A friend of mine used to have a five gallon UGF marine aquarium with two damsels in it that was beautiful. I myself have kept large local water marine systems on UGF alone. Other people like the gizmos and gagets and R/O units and inverts and stuff. Narrow down what you wish to invest in the tank so you can better determine what advice you need.
~~Colesea