You'll need to go to the 45 series of Beseler to handle over 6X9. I feel that I'm right at the comfortable limits running 6X7 in the 23C with cold light or dichro heads. There are entire darkrooms being given away or sold very cheaply. Most of the 4X5 rigs of most brands are honest pieces of machinery. Try to buy into a system that leaves you a reasonable chance of locating lens boards, carriers, light sources, etc.