My diagnosis is that he came from the roland vs-1880, which has really think, bright, even shrill preamps, to the Tascam which has cheap, yet 3 generations newer, electronics and he is missing the brightness that should have never been there in the first place. He thinks there is something wrong with the new stuff, because he is used to the old.
Unfortunately, in order to get the same I/O in the "superb" category, he will need to spend nearly 20 times what the Tascam's cost him. I am assuming that isn't realistic.
Your suggestions for audiophile home stereo equipment, two channel interfaces from 10 years ago and 8 channel tape decks from 20 years ago entirely miss the point of the op's question and situation. (Never mind the philosophical ramblings about what sounds good now vs. future, ancient stereo power amps, and the stuff you have in your collection that sounds great, but isn't plugged in)