I wouldn't use a cooltube on a CFL. CFL's don't produce as much light from a single point; it's a huge part of why there are more heat issues with HID lighting. (The fact that CFLs are able to dissipate heat more easily because of the much larger surface area for cooling is a big deal.) The flip side of this is that CFLs light lack concentration, even in large sizes. Less heat means you can keep the lights closer; lack of concentration means you have to keep them closer. You're going to lose some light from a cooltube, and you're not going to put the lights as close with a cooltube (unless you put the lights pretty much on top of the plants...which I don't think will be good either.) They're small changes, but they add up.

If you've got a small area--and if you're thinking about using 6 23 watt CFLs, I'm thinking it's pretty small--I'd go with multiple bulbs. Less heat issues, and you can get the lights right on top of the plants. I've always thought super big CFLs were kind of a mistake, FWIW.