There are few cassette decks that do a very good job of replicating the source. They cannot beat a good vinyl playback system but can hold their own. Nakamihcis, as good as they are, could not replicate the ambience and image like the vinyl source. The best decks I've heard in my system are Tandberg 3014s. They create better soundstage close to source.
I agree with Ralph, you lose bass with faster tape speeds. On my RtRs the bass is better at 7.5IPS than it is at 15IPS. The disadvantage of cassettes is the tape width, not enough real estate to put music down and saturate very quickly.
They're fun none the less.
