I've spent some time and effort looking at led lights, and demonstrated my findings at scaleforum last year.
Rather than a long, detailed and very boring post I'll make some suggestions, based on detailed colour readings and calculations.
Firstly, you'll get what you pay for! Some of the cheapish led tapes give very poor colour rendition, (tending towards a lack of green (no, you can't put a green filter over them, doesn't work like that. )). Many of the cheaper tapes also have a wide spacing and narrow beam, leading to a noticable pooling of light, especially when parallel to the track.
My conclusion was that the best colour and light intensity that I could find was to use two strips of bright white and one strip of warm white, this gave a colour temp of 5500k and a very even colour rendition. Some people commented that it was very bright, however, the numbers showed that it wasn't as bright as natural daylight, but will provide all the light that I need for my layout. 4ft x 18in. Having tried my lights out on a much larger layout, the owner has decided to go with a similar set up. A single strip of each of warm and bright white was tried, giving a good colour balance but not quite enough overall light on a large (3ft deep) area.
The power supply unit for my cameo layout would need to be a 36 watt supply.
The supplier that I used was led hut. Many others are available.
Cheers
Richard Lane