I have no experience with any Tascam desk, but large old analogue desks, which I do have some experience with, can be a maintance nightmare..
There's no point in spending a grand if you need three to fix it. I know several people who bought 'bargain' monsters only to find out the hard way that they can't afford to keep it running. Power consumption is also something to think about.
Makes sure it doesn't use custom faders/pots. If it does I wouldn't get it even for free..