I use our little mini system with a dub deck to listen to my wife's collection of some 300+ tapes. I do not patch it through the main system as the sound quality of the deck "and the tapes" are not that good. They sound "better" on the little system through Polk RT15 speakers. They also sound fine when played on the stock stereos in our old, older and oldest Honda's. I cannot think of a good reason to buy a better main deck to make dubs for use in the cars (due to their lowfi sound quality). And in the main system I would just as soon play a CD. I need to make dubs of her tapes as many are from the 70's and early 80's and they are going down hill very quickly. So, we really just need a deck to enjoy this old music library (mostly R&B and Disco) and to dub the old tapes onto new stock. Their are some very high quality cassette decks that come "close" to the sound of vinyl, but what is the purpose if you are dubbing from CD? If I wanted better sound in the cars I would just install a modern CD player (all in one unit with amps) and new speakers at a very reasonable cost. Since we don't mind lowfi in the cars the little dub deck and the old tapes are fine. I recently ran across a Tandberg 3014 deck at the local pawn shop and went through this thought process. The deck was a steal at $950.00, but I found that I really did not need it. I would be better off spending the money on CD players for the cars. Also when buying used tapes you will find that many of them have been trashed from being played on cheap portable machines.
