So you're setting up a reef tank (coral, inverts and live rock make it a reef tank). Your live rock will be your biological filtration, you can use a wet/dry filter or a canister filter. Some of the wet/dry systems (like the tidepool) have a bio-wheel included in the system, but live rock will accomplish that task.
I have a 55G with a canister filter and live rock, it's a reef tank also. The canister filter is basically just to hold the activated carbon and filter floss for filtering out stuff. So again, my live rock is my bio-filtration.
I have two maxi-jet 1200 powerheads, they're 295 gph
and I'm about to add a third on advice from the forum, so your 2x250 is a good start. The lighting will depend on what kinds of coral/inverts you want to add. If you get those that don't require intense lighting, you can go power compact, they're good and not so expensive. I have Current USA Orbit flourescents, 4x65Watts (two daylight, two actinics) I don't have intense light-requiring corals, but I have some branching anchors and candy-canes and an anemone, there are other things I could add that would be interesting with my lighting.
You can get dry sand, like aragonite, and add or not add a bag of live sand, that's up to you. I did that and it worked for me. You can add live rock and not worry about worms that will kill your fish, I don't think it's all that likely, but if you're really worried about it, Petco and Pet Club and I'm sure there are other lfs
that have cultured live rock. It's basically cultivated in captivity, so it doesn't come in with anything in it but the bacteria you need to process the ammonia and nitrites. I've used "real" live rock and cultured and they both work.
If you don't have much experience and you want a good reference book, pick up a copy of "Saltwater Aquariums for Dummies" and read through it. It was very useful to me. One thing they recommend that you don't need is an air pump and air stones, but everything else is good. It tells you step-by-step how to set up the tank, cycle it, stock it, maintain it, how to pick the right fish and what equipment you need for the type of tank you want.
Don't rush, take your time, you've got the right idea there. Also, check out the "Articles" section of this forum, there is a lot of info there also.