HI Joey...I'm only in the nano-reef biz, but, maybe I can help a little for now:
1) first off, the easy stuff, the heaters should be fine. Heaters are good for SW or FW
2) The filtration on a saltwater tank is your live rock which is the big investment for a tank your size. At almost a hundred lbs of LR or more, it's a big step. Some people build a PVC scaffolding to put the LR against to improve flo-thru and reduce the expense and volume of rock.
3) The filters should be/ could be exchanged for powerheads. Water circulation is one of the most important features in a SW tank. You might even add a wave maker in the future depending on your stocking/inverts. Overfiltration can lead to a build up of nitrates, hence, many don't use filtration canisters.
4) Something the FW people are not exposed to that much is that a SW tank needs a protein skimmer..it removes DSO's (dissolved organic acids) from the water which can lead to algae overgrowth and nitrates.
5) if you want to minimize your headaches, using RO/DI water (reverse osmosis/deionized) is most optimal. Well water could contain heavy metals, phosphates, etc. You can have your water tested to see where you stand. You want to stay away from phosphates, a big headache when it comes to algae blooms.
6) Lighting is the most complicated question (why I left it to last). If you are only planning on FOWLR (fish only with LR), lighting is unimportant and what you have is fine. If you are planning on having corals, some require intense lighting, often greater than 3-5 watts per gallon. At 135gallons, you'd probably need 2 metal halides if you plan to keep the toughest corals, SPS, soft polyped stony corals, or a more compact fluorescents, too detailed to get into in one post. I don't think your present lighting would support even the basic corals very well.
Search amazon.com and look up Paletta's book on starting a marine tank and Kurtz's book. They are great starters. One thing I recommend is doing a lot of reading before cranking up the tank. Good luck. SH
