is a 555:1 impedance ratio ok?

You'll probably hear a lot of different opinions on this. IMHO while not ideal, it should be OK. Cables can have some influence here. Another consideration when mixing tubes and solid state can be DC leakage. What do you have in mind?

i hava a classe ca-200 and am thinking of getting an anthem PRE1L.

something else i've been wondering about... i'm using thiel 3.5s that come with a bass EQ box that goes between the pre and power amps. what effect, if any, would this have on impedance matching? does this complicate matters?

In that case, it's the Theil EQ box that's driving your power amps. The output impedance of your preamp is irrelevant as far as your power amps are concerned. The Theil EQ box will eliminate any direct interaction between preamp and power amps. I expect that the EQ box, having a solid state output stage, has a pretty low output impedance (have any specs on it?).

I think you'll be fine with this configuration.