Howard, the info in the previous posts is very misleading if not totally inaccurate, as I intend to explain...yet again. Links to information as you asked for will be provided in what follows.
Photosynthesis uses light in the blue and red colours of the spectrum, and reflects light in the green. This is a scientific fact. The first link is to an article from the Tropica plant site in Denmark, written by three Europeans and which first appeared in the publication The Aquatic Gardner, volume 20(2), 2007, pp. 26-35. The Aquatic Gardners' Society is highly respected in the field of aquatic plants, and Tropica Nursery is similar, employing professional botanists who understand plants. This is an excellent article on this subject.
The second link is to an exchange on the forum of Acquatic Plant Central but the first post is very detailed, and others follow (for 11 pages).
Lighting Spectrum and Photosythesis - Lighting - Aquatic Plant Central
I could cite dozens similar. My conclusion is simple from the facts. Plants most need blue and red light, they reflect green. But blue and red alone creates a purplish hue to the aquarium which does not render true colour of plants and fish. Adding the green balances. Full spectrum best achieves this. The sun at mid-day has a colour temperature of around 5500K, so a tube close to this will probably be natural, although they can vary because of particular emphasis in the manufacture.
Where there are two tubes over a tank, one can mix a full spectrum with a cool white to achieve what scientific studies have determined is the best light for plant growth. In a test that I mentioned in another thread, plants responded with the best growth to a mix of full spectrum and cool white, second best to cool white alone, and third best to warm white alone. The evidence speaks for itself. The test appeared in the July 1987 issue of FAMA, in an article by K. Richards, pp. 16-20, and was cited in Diana Walstad's book, Ecology of the Planted Aquarium
, should you want to track it down.
All of these findings over more than 20 years agree on the science and hundreds of aquarists have observed the obvious results of following the advice. If you want to see my tanks as proof, check the photos under My Aquariums. This is what some term low-tech, I prefer the term "natural" aquarium because it makes the most use of nature with the least amount of interference by the aquarist. If you are aiming for a similar style of planted aquarium, it is easy to achieve at little expense.
To your initial question, 96 watts over a 50g is high light in my view; I would aim for no more than 1 watt per gallon without CO2 which is what I have over my three tanks. The plants that will thrive under this system are the majority; those few others such as some of the grass substrate covers and such need more, and probably benefit from added CO2. What you need to spend on paraphernalia depends upon the type of tank you want in the end.