My first planted tank was a 10G and I ran both 2x15 watt and 2x26 watts and can speak to both.
First, I think a 10G can be a great option, and if you haven't purchased your tank yet I would recommend you strongly consider the hoods with the standard screw in bulb fixtures. The appeal for me, at the time, was that no modifaction to the hood was required at all. I simply removed the stock bulbs and put in the CFs.
On to wattage....I started with 2x15 and DIY CO2 and had good steady growth. I kicked it up to 2x26 and did great, but battled algae pretty consistently. I would recommend the 13 or 15 watts in the stock hood like mine, but if you don't mind taking on the algae than 26 watt was by no means a plant killer.