I'm running my 604's at a crossover point of 1150.

[amandarae]

I still haven't built my XOs yet. After reading this thread I might try bi-amping my 604Ds with my Behringer DCX2496 first. Problem is I don't have enough amps and don't want to cannibalize my daily system to experiment. I might build another one of these: Transcendent Sound Cathode Follower Tube Amp and use it along with the one I have running my BR TV system to play with the 604s. They are a really sweet 3W/ch and I think I had around $500 all up into the scratch build of the first one. That's pretty cheap for a pure SE tubey.

You should check out TubeLab SE and Tubelab SE as well. You can build the amps at almost the same cost($500, or much much more depending on parts and transformers use), but the SSE can use 5881, 6550, KT66, EL-34, 6L6. I built several amps, and to me the Tubelab is the closest sounding Triode strapped Pentode SE amp to a true DHT SET amp using 45,2A3, and 300B(all of which I have). Excellent sounding with my Altec drivers. I am not affiliated to Tubelab by any means, just making a suggestion.

My amps
http://imageshack.us/a/img9/853/tubelabamps058.jpg SE(581/300B) on the left, SSE(using EL34) at the right.



Abe