In the 200mm range, there are a lot of options. What sort of lens are you looking for? Old, new, coated, not, convertible?

As someone mentioned, the 203mm Ektar is a joy - I have the 203mm f7.7 Kodak Anastigmat, which is an early, uncoated version of the Ektar (its a dialyte type lens, and is actually at its sharpest wide open). That lens, in an old rimset Compur, lives on my speed graphic. A cheap option is the Ilex Acutar (you might find it in a Copal 1) - 215mm f6.3, Tessar type. There are newer, Caltar versions as well. Nikkor lenses are beauties (I sold my 150 to raise cash but kept the 90 in Copal zero). Dagors have a distinctive look, tons of coverage for their length, and are convertible - I use a 5" on my Speed for landscape work and a 9 1/2" on my 8x10 for everything from landscape to portrait. Turner-Reich convertibles are a favorite of mine in all formats - they're triple convertibles - I use a 6"-ish lens on 4x5 and the 12-21-28 on 8x10. Protars are another nice convertible. Then there are the oldies - Aplanats, Rapid Rectilinears, etc - nice old look for portraits but most dont have working shutters (or came in barrel) so are better suited for a Speed rather than a Crown.

As you mentioned, play with the Xenar for a bit and see where you want to go from there. You may find yourself hampered by the shortish bellows on the Crown and want something with some more draw. Or, you may want the focal plane shutter to use barrel lenses. I wouldn't rush to do anything yet. The Xenar is a nice lens.

Dan