I'll jump in and add one (probably controversial) comment, and that is that Yes, cold light heads (or other diffusion sources) are catagorically better than condenser heads. Condenser heads are much harder to keep clean, more difficult to control delicate contrast with, magnify any dust anywhere in the light path, and generally suck. (Yes, this is totally my personal opinion and not entirely objective. But my remarks are based upon 20+ years of printing experience, 10 as a professional lab technician.)
Most modern cold light tubes are fine to use with variable contrast papers. This was not true 20 years ago. Even if you get a second hand head with one of the old blue tubes, you can replace it with a modern green one which is appropriate for VC papers, with filters.
VC heads with dial-in contrast filters are great. I really love the Ilford 500 system, which is a diffusion head- not a cold light. It's powered by halogen bulbs reflected though glass filters (which give contrast control) and a white mixing chamber, before being further diffused through a piece of white plastic just above the negative carrier. This system is really nice, and delivers a consistent amount and quality of light every time. It offers contrast control and time control from a single seperate keypad, which is great since you don't have to touch the head once the negative is in place. This makes split contrast printing a breeze. Too bad they stopped making the 500 system years ago. Variable contrast cold light heads work in a similar way- just make sure you get a stabilizer for consistent results. VC heads are a pleasure to use, and are quite simple to operate.
I agree with Benjamin that an Omega D is better than a Beseler. The Omegas are very solid and easy to align, and unlike the Beselers, they seem to go out of alignment very seldom. Second hand enlargers are going for a pitance these days. Check Pnet, craigslist, eBay, and your local photo stores, and be patient. The right one will show up. I have three Omega D5's, none of which I paid more than $200 for second hand. I bought one off of eBay last year, with a dichroic head for $100. Even with shipping it was under $175. Expect to get a chassis and put the head you want on it. I don't think I have ever bought an enlarger with the head I want to use. Second hand ones always seem to come with (useless) condenser heads, which I dump. I sometimes use the dichro head for B&W printing, but as soon as I can find another Ilford 500 set up or a good VC cold-light head for it, I'll switch it out. (Any one want a D5 dichroic head cheap? It has a power supply and a timer...)
Anyway, both Aristo and Zone IV make good cold light heads. (Is Zone IV still in business?) If you can find/afford a VC unit, do it; otherwise you can use seperate filters, as long as you have the right bulb. Cold light bulbs are fairly cheap and last a ridiculously long time.
Whatever you do, good luck and have fun (and stay away from condenser heads! 😀 )
