I have a Kaiser VP6005 which I use for colour work. As your enlarger will cover up to 6x6cm you will need a 50mm lens for 35mm and an 80mm lens for medium format. I can recommend the 50mm f2.8 EL Nikkor for 35mm and the 80mm f5.6 EL Nikkor for MF. Both are 6 element lenses and have a well deserved good reputation. All things being equal they will turn out first class prints.