depends on what you're looking for...
anyone seriously looking at ti bikes would have to include the three I mentioned. colnago makes 2 ti models and lemond makes at least one.
the serotta ottrott is arguably the finest bike made. serotta's legend ti is also a fine bike. I would lump serotta in with the smaller, custom-type makers you mentioned. all fine bikes.
colnago needs no introduction. the lemond ti is one I don't know much about, but it is ti and another option.
if you want a one-of-a-kind, not much chance of seeing another, on your club ride, then go with seven, if, or serotta. if you're looking for artwork you can ride (and no chance of meeting another one), the merlin cielo must be considered - carbon tubes and unmatched sculpted ti lugs; its beautiful.
if you're looking for a performance racer, litespeed is the serious choice. the vortex and ultimate have been ridden to numerous professional victories, both in the us and in europe. many euro pros ride a rebadged/repainted vortex; lance rode one in his first tdf victory.
lots of options. depends on what you're looking for...