There is varying wattage on the CFL replacements, I typically aim for something around 15-17 watts as the bigger ones are often too wide to fit into the fixture itself without modifying something. But as with any DIY thing, your mileage may vary.
You can grow most plants with sufficient lighting. The plant growth will not be explosive like it would in a co2
injected and regularly dosed tank, but the plants will still grow. I grow all kinds of high and low light labeled plants together with low-medium lighting and no co2
and rare ferts. They don't grow super fast, but I don't really want them to.
The hard part comes when you have too much light and not enough co2
and ferts to accommodate it, this is where you'll typically run into algae issues and whatnot. There's a potential for this when you step up to the CFLs, so you may have to act accordingly if you start having issues.