You might very well get the sound signature you prefer by buying one of the current class D with a tube buffer on the input, giving you a modern solution to the problem. If you prefer vintage electronics, might I suggest a Hafler DH-200. This particular model uses Mosfets in the output stage and there are still many of these left in the used marketplace. Further there a few different resources for 'upgrade kits' that are said to increase sound quality quite a bit. Given how good they are right out of the box, improving on the basic performance would put it in rarified company.
