I've been using the same 23CII since 1971. They work. If you can find a good 4X5 enlarger for not too much more money, it will give you more flexibility and to opportunity to go LF if you want to. But be sure you can get a 6X9 negative carrier for it. They are definitely available for Beseler and Omega and are probably available most other major enlarger makers. You will probably need a new lens to cover the area. 105mm is standard for 6X9. 6X9 (or 2-1/4X3-1/4, if you prefer) is an interesting format. I've used it a lot in the past 30 years. It is the same as 35mm, only 6 time larger, with proportionally less grain and more detail. The negative size, like 35mm, doesn't correspond to any standard paper size, but the proportions are pleasing for many prints.