is a 555:1 impedance ratio ok?

Drubin is right. The active circuitry in the EQ isolates the input impedance from the output impedance.

The answer to your question is no. The output impedance of the EQ box is independent of the pre-amp feeding it. Or it should be.

i'm not sure if this posted correctly before, so forgive me if this is a double.

does the output impedance of the EQ box change if i switch between two different preamps with different output impedances?

i think i need clarification on the relationships between input/output impedances when components are connected in chains.

Yes, you need to match the preamp to the EQ box. I don't think you'll have any problem - the input impedance will likely be at least 75K, and as others have mentioned, that is high enough.

Good luck.

I dont have the specs but i can call thiel tomorrow... unless someone else has them.

so do i need to match the preamp to the eq box? i wonder what a desireable pre/EQ box ratio is.

EQ box or no, the ratio of 135 ohms nominal output impedance to 75K ohms nominal input impedance is plenty high enough of a differential ratio to negate the possibility of matching problems. In fact, 135 ohms output impedance is on the low side for an all-tube preamplifier, though it's a safe bet that the quoted figure actually rises at the frequency extremes, and 75K ohms input impedance is on the high side for a SS amp. Still, even if the pre output figure were to hit a couple of thousand ohms in the bass region, you would probably not hear any ill effects as long as the amplifier input impedance were about 20X greater, which yours apparently surpasses.

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.

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?

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?