To my knowledge, Naxos releases are available only on CD. Too bad -- I'd like to hear some of their better recordings on LP as well.
I have ordered Naxos releases online from Tower, although much of their stock on this label seems to be special order. If you have a Barnes & Noble bookstore nearby, they carry a fairly wide selection of Naxos recordings (my local B&N has about half of the composers in the Naxos catalog represented). (I haven't tried B&N online, but I'd bet you could also order Naxos CD's from them.)
Naxos releases have a MSRP of $6.99, although they are sometimes discounted to $5.99. At these prices, it's fun to experiment with material that you might avoid at $15-18 per CD.
As I said in my first post, I have purchased only a limited number of Naxos releases, although I intend to buy more based on my experience thus far. This week I bought a copy of the Joseph Martin Kraus release (#26 on the list above), and it's a superb recording in every way. Kraus was the major composer of the Swedish royal court, and a contemporary of Mozart, and the 4 pieces recorded on this CD (an overture, and 3 short symphonies) are wonderful. In addition, the recording quality is first-rate (infact, this recording would do credit to any of the major and/or audiophile labels, IMO). I highly recommend this CD if you like Baroque music.
The recording of Bruckner's Symphony #3 (#11 on list) is also very well done -- fine music, and an excellent recording, with good ambience and audio quality.
I also purchased the William Walton CD with his concertos for violin and for cello (#47 on list above). While I have limited taste for most 20th century classical music, I liked this CD a lot. Not too much dissonance, and very fine playing by both the soloists and the orchestras. Another Naxos that is worth acquiring, particularly if you don't have much knowledge of Walton's work.
A minor editorial comment: as audiophiles, we sometimes fall into the elitist trap of assuming that inexpensive means mediocre -- particularly where audio equipment is concerned. This logic sometimes applies as well to our biases about recording labels. It would be unfortunate not to try some of the better Naxos recordings, such as the ones on the list. Much to gain, little to lose, it seems to me....