If you are as "sick" about this hobby as most of us in here seem to be then you will probably be looking into a bigger tank soon enough. I started with a 20g and before the year was out went and bought 125g. Absolutely no regrets.
As for the lighting, depending on what type of corals you want to keep allot of corals can do quite well with moderate lighting. Stronger lighting is required mostly for SPS (small polyp stony) corals, with a few exceptions in the other categories as well. My 20g has simple T5 (NO) lighting and my corals are doing very well.
Here's a link which may prove useful as to lighting requirements.
Corals
The mere fact that you are remotely thinking about a bigger tank tells me that you will be posting pics of your new 120g (to say the least) when you move in to your new place. Hey, if you have the room and you love this hobby, why not?
Good luck habibi!
