If it's single ended about 5-8 wpc. If it's push pull (2 output tubes) about 10-12 wpc. This is per channel. Most are single ended. Low to high medium loudness, they sound nice, but that's all they got usually. Unless it uses something other than EL 84s, like EL 95s, then it will have a little more balls. A decent tube Magnavox will blow them out of the water, volume wise, although the German may very well sound better at lower volume.
Some used electrostatic tweeters which will most likely be dead by now. The other speakers they used were nice sounding, just not made for high power and won't work real well with anything other than the amp they came with.
Many techs do not like working on them. In my opinion, they are not fun, but I've seen worse. Stringing the dial is a nightmare though. Other common problems are intermittent connection problems with push buttons and the power switch and occasional capacitor problems common to anything this age. The transformers are usually pretty robust.