Welcome to canreef and welcome to the addiction
If you want to keep it simple, I'd say focus on these important things:
- your lighting
- good skimmer
- sufficient liverock
- a sump
- either the dedication to dose your calcium/alkalinity daily, or a system to do it for you
- a sump
or you can run a sumpless and skimmerless system if you feel daring enough.
those are the most imporant things and you can keep those simple as well.
Lighting your tank, because of it's long and narrow dimensions, would be best with T5 lighting. I'd recommend a sunlight supply fixture. If you're planning on softies and LPS (like my own tank), I'd recommend a 4 bulb fixture (four 72" lengths of bulbs). Make sure they're High Output (HO) driven and have individual reflectors for each bulb (so in other words, NOT the coralife fixtures heh). The PCs you have now are not enough, and if you were to add more, I'd just recommend a new fixture. The 6' length would make finding a proper length fixture hard. You COULD run two 250W metal halide bulbs if they're up high enough with a good reflector (a PFO parallel or something). They should be good for most softies. It would be cheaper to DIY. Some stuff would have difficulties in the far bottom corners though, and the middle bottom.
Next to your liverock, your skimmer is your most important means of filtration. Do your research and don't skimp on it. Go for something a little bigger than what you need too. I recommended the sump, because it opens up your choice of good skimmers drastically. Be careful, some brands are truthfull in their rated values, while some are enourmously overzelous in their skimming capabilities. (unless you go with a skimmerless system, explained later)
I'd recommend getting in touch with reefers in your area, or maybe keeping an eye on any local buy&sell papers for people selling liverock, or selling entire systems. You can get liverock for much cheaper than the store from a fellow reefer (or ex-reefer if they're selling or piecing their system out). If you can find some of good quality though (not overgrown with macro algae, covered in undesireable polyps, etc).
Like I said, a sump is VERY beneficial for a reef tank. You can put a skimmer in it. It keeps the display tank's water level even. It just makes everything so much more simpler. Plumb it off the back, instead of the bottom. You can keep it even simpler by drilling for your drain, instead of an overflow.
As for dosing, you'll have to maintain your calcium. You can go cheap, and mix kalk or two part mixture every day. I hated the daily chore of top-off, so I made a ghetto style DIY air driven top-off that doses kalkwasser mix for me. Plenty enough calcium for soft corals and LPS. You can spend the moolah on a litermeter to do it for you if you want, too. Just keep in mind it gets tedious to do it every single day, and if somone misses their dosing the animals feel it. If you're looking at something automatic, dosing pumps are the simplest to run, and for the same price as a high end calcium reactor, you get something MUCH easier to setup, and very easy to adjust down the road as your calcium demand changes. (no dosing required in a skimmerless system. more later)
And a sump. Did I mention a sump? lol
(i know some of you run sumpless and go you; i just know there's so many others that swear by their sumps. unless you have a skimmerless system. more later lol)
Whatever you do, you'll wish you had done some things different 6 months after you set it up
The gung ho attitude is great
You probably have an RO system if you have a planted tank, unless you have soft water in the first place. If you do have the RO, add a deionizer on a valve you can turn on for your saltwater, and turn off for your freshwater.
Oh!
Oh yeah! skimmerless systems! If you want to go REAL simple, you can do some research on skimmerless systems. They do weekly water changes, and it's quite doable if your bioload is kept way down (fewer fish, more inverts). You'll go through a lot more RO/DI water, and a lot more salt, but you'll have a more natural system, and dosing would be almost unimportant because your salt mix will maintain everything. Weekly 10-20% changes are usually sufficient to run skimmerless. Your liverock will take a lot longer to cycle though if it's not cured in any way in the first place.