Beseler 45's, Omega "D" series, and, to a lesser extent Saunders LPL 45xx, enlargers are common in the US used market. Of the bunch, I prefer the Omega machines; not because I think they are any better or worse than the others, but because there is a wealth of information and spare parts available for them. Harry Taylor has a web site at
http://www.classic-enlargers.com/, and can provide many parts and services for these machines. I'm a satisfied customer.
For a lamphouse, don't discount using a color head with built in dichroic filters. These are available, often for less money, than comparable condenser type lamphouses and offer a couple of very distinct advantages. For starters, the magenta and yellow filtration can be used for contrast control with variable contrast papers. Once you get used to it, you'll not want to start messing around with discreet variable contrast filters. Being diffuse light sources, they are more forgiving of small flaws and dust specs. Small scratches to the support side of the film will often be completely invisible. Any dust specs or fine scratches that do show will be fairly easy to spot out. Of course this doesn't mean that a diffuse lamp house allows you to be completely careless about cleanliness. It just makes things easier.
You might read that condenser type lamphouses produce sharper images. Pure nonsense. Sharpness, or more accurately resolution, is determined by the quality of the lens, the accuracy of focus, and the alignment of the machine itself. They do provide slightly, and I do mean slightly, more print contrast than a diffuse light source, which can give the impression that the print is sharper than it is. This is inconsequential, and can be compensated for by using a bit more magenta filtration in the light path or simply by developing your film to a slightly higher contrast index by extending the development time a bit.
Lenses are a hotly debated topic. Here's the skinny. Any of the six element lenses produced by Nikon, Schneider, and Rodenstock are better than good. There are some other brands out there that are likely as good. Some of the Rokkors and Fujinons are real sleepers and perform just as well as the equivalent lenses from the big 3 manufacturers. Don't get yourself into fits over which to choose. Simply avoid the entry level lines of lenses, and you'll give up nothing in image quality. For 35 mm. work, you'll want a good 50 mm. lens. Medium format negatives, up to 6x7 cm. can be handled with a good 80 mm. lens. For 4x5 work, you need to look at either a 135 mm. or a 150 mm. lens. The 135 mm lens will give you a little bit greater enlargement than a 150. From Nikon, the high quality lenses are the 50 mm f/2.8, and the 80 mm. f/5.6. They did not make a budget quality lens for large format work. Schneider's Componon-S series of lenses and Rodenstock's Rodagon series are the equivalents. Avoid Schneider's Componon (no "S") and Rodenstocks Rogonar lines. They are good lenses for modest enlargements, but they are not top of the line. Lenses designated "APO" are extreme high performance lenses, that are often touted as being the best thing to come along since sliced bread. That's true if you go in for enlargements greater than 10x or so and demand the utmost image quality. It also means that everything else, and I do mean everything, in the chain is equal to the task. If there is a slight misalignment of the enlarger, a slight misfocus of the enlarging lens, a less than stellar taking lens on the camera, a little bit of camera shake, or any one of a number of variables that are not completely perfect, the whole point of using an APO lens is nullified. These lenses command a price commensurate with their reputation. It is often money not well spent. You'll do better to invest in a good grain focusing microscope to insure that the image on the baseboard is truly in focus, and not almost in focus.
