That $500 is just the beginning. Lighting CAN be much more expensive.
Sumps are cool because they allow much more flexibility and versatility to the types of filtering. The basic rule of thumb is to keep the surface area for bacterial organisms high. The sump allows for this with the bio-balls as well as adding LiveSand, an air stone, or other media to keep up the "good" bacterial growth. Sumps are costly but very effective.
The bulb to get will be the one that suits your needs. I have the 10k and everything in my tank lives happily, not signs of stress, and eats very well. I have a FOwLR setup. The only reason you would need more spectrum is if you had corals, clams, and various other reef creatures.
-Jason
~60 gal Tank
Eheim 2215
UV Filter
~70lbs live rock
Brittle star
Sea Urchin
Two cleaner shrimp,
YellowTail Damsel
Singapore Angel
Green Chromis
Banded Clown