+1 to that, although I didn't try the Markbass on a rehearsal, I could see how that could work as there is greater clarity.
On the volume/wattage debate, I found this on a website and I couldn't say it better myself:
"Bear in mind though, that there are often other factors that make a difference. Playing in a band with an amplifier that is slighty underpowered for the rest of the band is nearly like playing without an amplifier at all. So playing with an amplifier that may be only 3dB louder (double the power) may be just enough to be heard properly, and make all the difference."