In my opinion German M42 lenses are vastly over appreciated currently. I've used lenses from most of the German companies, Enna, Isco, Schneider, Schacht, CZJ, Meyer... and honestly most of them are just o.k.
Especially the West German lenses, keep in mind that the West German camera industry collapsed during an era of rapid improvements in lens design and that a lot of the lenses that were available from these companies in the 1960s were designs from the 1950s. This is especially true for wide angle designs.
There are some good wide angles, I like the Schacht Travegon especially - but honestly it's not any better than the 3.5/35 Takumar and it will generally cost you more, and likely not work properly when you get it. The Schneider wides are also good - but again you can find Japanese lenses just as good for the same cost or less.
I only kept one W. German wide, an Enna 3.5/35 which is not particularly good, but I personally like the rendering it gives.
The E. German lenses range from awful to brilliant, but on the whole are cheaper than their less common western counterparts. Just watch out for petrified grease, especially in the Zeiss Jena lenses (less of a problem with Meyer lenses).
Japanese lenses are commonly overlooked. Fujinons and Yashinons - Mamiya Sekors... just watch out for the ones that were designed to couple to camera meters with a proprietary linkage, some of the Fujinons and Mamiyas will not work with adapters.