My advice would be to try before you start looking for a new lens. Sufficiently large trays are of course a nice thing to get but apart from that I would make some prints before I would go out and buy anything else. 20x24" might be a bit too large from a 6x7cm neg but it could work (about 8x enlargement which is a little more than I would do but then there are people making 11x14" copies from 35mm negs and being happy about it so why not).

Best of luck