you could ignore the corals all together and go with a FOWLR tank instead. you won't need the expensive lighting and there is a little more room for error. FOWLR means Fish Only With Live Rock. The most expensive things i've bought for my tank are the skimmer (hardly use now, 2 or 3x's a week), 2 canister filters i bought (at an LFS for more than double what they cost on the internet
) and Live Rock (LR). The LR is the most essential part of the filtration. in one of my canister filters i've taken out all the media so i just use it to add more flow to the tank. I've also been thinkin about doing it to the other canister as well. You are also going to want some powerheads, most people aim for a flow of 10x's the volume (120g tank generally needs a minimum of 1200 g/h turn around). Also, you will want to get the biggest tank you can afford/fit. With a bigger tank you won't have as drastic of fluctuations in your parameters.
As for is saltwater better than tropical...well you're in the saltwater section so our replies might be a little biased
. I have my 45g freshwater tank in my bedroom because there is no room out inmy living room for it. I hardly ever pay attention to it now (
i feel horrible about it too), but i'm always looking in at what is going on in my saltwater tank.
just to reiterate what everyone has said/implied, research is very important. I did 3 months of research before i bought my tank, and another 1 or 2 before I actually purchased my LR and started cycling my tank...after all that i still don't think i did enough research. I ended up getting a "tall" tank and realized the fish i wanted (volitans) could get as wide (tip to tip) as my tank. that would seem to comfortable to me, so i ended up with what i have now. I also got a shrimp that I thought was a cleaner shrimp only to find out that it is predatory and has killed at least 1 of my fish so far and now can't feel comfortable getting a fish i've been hoping to get after my tank had been established for a year (green mandarin). Good luck in whatever you decide to do, just make sure you figure out what you want and what it needs