Another vote for the Beseler pair. Frankly, if push came to shove, I'd keep the Beseler 45 MCRX and let all the rest go. You could pick up a dichro head for it for around $300 +/- and you'd have everything you want to do covered (variable contrast, color, b/w, 35mm, 2 1/4, 4x5) that you can do with an enlarger. If you really want to keep two, I'd keep the 23C and the 45MCRX. The Beseler 67 and Omega B600 are fine if you need a lighter-weight enlarger that you can move in and out of a temporary darkroom on a regular basis, but they're not the most stable in the world. I currently have a Beseler 45-series enlarger, and a 23C II (I think it's an XL, but I don't remember - it's not currently in use). They're both solid as rocks (the 23C was an enlarger of choice for many school darkrooms, so that ought to tell you something about how rugged they are). I just don't use the 23C because I can do everything it does with the 45, and more, and the space where it was is now taken by my UV exposure unit. The one thing that would be convenient to have interchangeable between the two Beselers that isn't is the negative carriers. Not a big deal when you're only shooting 1 or 2 formats, but when you get into 6x6, 6x7, 6x9, 4x5, 35mm, and 24x56mm (Xpan negatives), your negative carrier collection explodes. But yes, the lens boards are interchangeable between the two.