I've looked at this driver a few times, nice, inexpensive and well built. Although this looks like it may be a slight variation on the stock driver. Looks like Audio Alto did a nice job on the cabinets, But to reiterate what Ralph said.... You need a minimum of around 95db sensitivity to use a small tubed set amp and 100 is better. These are rated at 85
The Audio Alto R101 : A special speaker for SET amplifiers and small acoustic spaces
My review on the Audio Alto R101 speaker just went up on the Stereo Times website. It was a pleasure to review this "petite" single driver floor-standing design because of it's overall beautiful musicality, amazingly good overall dynamics, and finally it's excellent top and bottom frequency extension. If you love tube based SET amplifiers or low power Solid State amplifiers (think Pass Labs XA-25) and have a relatively small acoustic space this might be a great speaker for your system. Take a look at the review for all the details that led me to this conclusion.