There is at least on post on E 300s here at AK.
The 300s don't have the midrange that the 302s have, so I think they suffer incomparison, and the tweeters on both models are bolted to a plate across the woofer, so the tweeters are low to the floor, and if you you aren't seated or far away, treble may be attenuated - hence the add on tweeters.
The 312s are in smaller enclosures, so need more power to have much low end, but they do have the midrange, and power is much cheaper and more available now than when the speakers were made (and 20 watts per channel was a decent amount of power). Some of the smaller Bozaks used the same woofer as the bigger ones, but that meant that the low end was deficient, so later ones had woofers that were doped to increase mass. This gives more bass depth, but at the cost, at least to my ears, a soggier bass.
Bozaks are among the standout speakers in terms of naturalness, and they also usually offered an upgrade path - your E 300s may have a blanked off cut out for the midrange, so that owners could add it when finances allowed. The crossovers needed to be changed to do this, but they, too were set up for this.
I have had many, many, speaker pass through our dining room, and Bozak 302s and JSE Infinite Slope Model 1s were the only ones that my wife and daughters complained when I moved them on. They are all musicians - I am not - and I trust their ears.
