I am familiar with the Tape Duplication business (the firms who churn out commercial releases). A Nak will do just fine on pre-recorded music tapes. Yes, it's capable of outstanding quality when given a source and asked to make the recording, and yes, the commercial tapes you will be using are of lesser Sound Quality (SQ) than what it could do given the same source on CD or LP, but they are what they are.
Generally speaking commercial tapes are made on moderate quality Normal Bias tape, with the cheapest possible case (which, in any cassette deck, forms part of the mechanism, versus, say, an open reel machine whereby it's just the tape itself and the entire mechanism is the machine only) so that affects ultimate SQ.
Also, with the cassette format being somewhat dependent on the mechanism being partly contained in the tape housing itself, and this is true of pretty much any cassette machine, the tape width being quite narrow, tapes will always sound best on the machine used for recording; there are small alignment issues that affect the Signal-to-Noise to some extent. It's not huge, but it's there.
The final thing that you have to realize is commercial pre-recorded cassettes were intended (like all music formats and releases) for the widest possible audience. So, things like Dolby NR isn't always employed, so that the cheapest portable machines could play the tapes, because that was the majority of users, not people with exotic tape machines. Thus the normal bias tape (leaving aside for the moment that record companies are notorious cheapskates, so it was used because it cost the least).
Also, making the tapes themselves (in companies known as "Tape Duplicators") has to be done more-or-less in real time (versus CDs and LPs, where you could crank one out in the time it takes to read this sentence).
The big "LA" duplication firms use technology (of course) to minimize the production time. Firstly by recording both sides at the same time (two masters, one played backwards) and by recording the tapes at what amounts to double speed (if you control the speed of both the master and the final product, you can manipulate the speed any way you want, so probably not exactly double speed and possibly higher, but there is a SQ limit so they did show some restraint)..
The trouble with that is bass response falls as tape speed increases (this is true of all tape machines, but open reel units can compensate with wider tape. None the less, even on an open reel machine, best bass response is with a slower speed versus 30 or 15 IPS (Pro and Consumer top speeds, respectively).
Back in the day when cassettes and LP records and CDs existed side-by-side, manufacturing cost went LP > Cassette > CD in that order. About $1.25 > About $1.75 > About $2.50. After some time, the CD format continued to be less and less expensive to make, so by the time the mid-90's rolled around it had fallen to become the least expensive. But, as I said, record labels are notoriously cheap. The tapes came in boxes, no cases, with labels on a roll and by themselves cost about 50c each (the rest of the cost being production costs of one kind or another).
The label would print their own cassette labels and liner artwork and the whole shebang would be assembled with cases into a retail package. Now take note that a quality blank cassette retailed for about $5, and manufacturing cost, remember they had no cost to put music on the tapes ... would still be more than that of the entire pre-recorded variant. So, perhaps five times what the blank cassette itself used for commercial releases cost. Note that the blank tapes were made by the same companies; that cost difference isn't some hidden profit "bonus".
Having said all that ( I hope you're not depressed by this point) Naks do very well on Normal Bias tape and the part of the mechanism they do get to handle in the cassette format is done quite well.
If you don't intend to do any recording, a 3-head machine is kind of overkill. A 2-head machine would do just as well as far as being limited to playback only of commercially recorded tapes. Although 2-head Naks are slightly lower in overall performance (and only slightly) they are none the less much better than the machine used to create your commercial copy.
You do get the tape handling advantages of a dual capstan drive, which is far from trivial, in a 3-head Nak but they also make some dual capstan 2-heads as well. So there is an opportunity to save some money if you want.
Naks work best with (are biased at the factory for) Maxell XLII tape*, but since bias is available on the machine you can set it up with any brand or type of tape. TDK SAII is highly recommended for a High Bias type blank tape.
* Nakamichi branded tape, not sold in North America but sold in Japan, was made by Maxell.
