If this were a smaller tank, Sam, I'd be in total agreement (sp), and I second the reading of the EI article and the other articles pinned here as well. But since Fillet's tank is so large, WPG is generally of little use. The larger the tank, the less light you can get away with and achieve the same results as a smaller tank with more light. There's a mathematical ratio thingy for this, but it's too early to turn on the scientific portion of my brain at this time and I need more Cuban coffee.
A 120g with 1 WPG has considerably more light than say a 55g with 1 WPG. I would suggest not upgrading the lighting for the time being and sticking to hardy species. It'll save you, Fillet, some money too. Hardier species will do very well with the lighting he (sorry assigning gender) already has and will still look great in your huge setup, which will look great anyway, because the tank is just HUGE!
Any upgrade, and he'll have to consider pressurized CO2, which he may have to do in the future anyway, unless you, Fillet, are like me, a yeast lover.
Your tank, Fillet, looks very nice. The black background was an improvement. The reddish plant in the center left might give you problems with the lighting you currently have. A general, and I mean general rule is that the redder the plant, the more light it requires, but there are always exceptions, which I have discovered
. I would also consider adding root tabs, especially for your amazon swords, which one looks a little pale and transparant to me. They tend to feed from their roots rather than absorbing nutrients through their leaves at the water column. Seachem makes a great root tab that lasts for three months, which I use for my crypts and root feeders, like barclaya (a flowering plant) and the lotus that you have in the back right (an example of a red plant that does pretty well in lower light). I don't think you have a nutrient rich substrate, right? Just gravel?
If you don't mind, I'll make a plant suggestion that will very useful if you can find it. Consider Egeria najas, a slender-leaved anacharis or elodea species. It has lovely, serated leaves and is very hardy and able to withstand higher temperatures. It also grows quite high and will provide a lovely dark green contrast to the background. Just an option. I loved it in my 15g in IL, and still miss it. I wrote a profile for it at TFF and really recommend it in a first-timer's planted tank.
I'm officially done now. Everybody breathe a sigh of relief!
llj