The 300 series covers a large number of Bozaks, some quite wonderful. The full size ones provide a very large portion of what makes the full size Bozaks so special -- relaxed, natural, warm and extended tone and dynamics, with realistic perspective.
The Tempo series, which is more normal bookshelf size, is less appealing -- the box is too small for the infinite baffle woofer, and to the degree that they go deep, they don't sound so relaxed. But the drivers are fine, and you could either enjoy them for what they are, or move the drivers to a larger enclosure (though they mass loaded some of the later Tempo woofers and so might be problematic -- they have a black coating on the woofer cone).
300 is not a steal for the lower end models, but also is not a bad price, maybe even good (I think), for a three way version and above.
But tastes matter, and they may be too soft for you if you listen to rock and roll mostly. Or maybe not -- I loved them on most music.