I never had the chance to play around with high-end Naks, but have had the BX300/150 as company for several decades now. My mentor told me that the cheaper Naks sound quite like the big ones, however the big ones can record much better. Also, while the lower-ends Naks can be maintained more easily, maintenance of the big ones is a giant challenge and money pit, and harder and harder to find someone who can maintain it. The Naks are a totally different league compared to Yamaha and other lower-end decks I had the chance to.... yet, what truly makes or breaks tape experience for you is the rest of the audio system.
They do not work well with modern mainstream systems, those make them sound like: unacceptable background noise, limited frequency extension, emphasis on wow and flutter, and make you cry for the safety and predictability of digital. Progress has not been kind to tapes. At all.
However, hook a BX150 to a high quality tube amp (without feedback), ultra-high efficiency loudspeakers, and prepare to be very much surprised. This type of systems approach does not place the noise in the foreground. You will notice that the concept of tape hiss becomes meaningless. Yes, it's there, just like a quiet fireplace is there on a winter night. Yet, apart from a sonically separate fireplace, the music itself has no noise component in it, and comes out very clear and fleshed out. I have a couple pre-recorded cassettes that just sound astonishing, even though they are normal bias, the noise is a non-issue, has not bothered me not a single time. This is hard to grasp as most systems turn the innocuous background noise into a poisonous gritty harsh foreground noise that is ground up with the music.... if you only heard that type of sound, then you have not heard tape yet... just a shadow.