I have a nanocube and its 24 watts. Its good enough to grow some plants, but now they have a deluxe nanocube and it comes with 48watts! The Deluxe system is 150 instead of 99 or 89$. BUT its well worth it! On such a small tank like this, 48watts would be growing anything!
I have a 12G JBJ Nano cube and find it to be a great deal. The 24 watts of PC lighting is plenty of light to grow almost any plant. I have grown Rotala indica, Ricca and a carpet of Baby Tears to name a few.