Depending on the output impedance of your cd player (or whatever is driving the 27 tube) why not try using a 10K to 10K input trans with a 10K series or ladder type volume control across the secondary of the input trans. We have a nice 10K to 10k guy that we just intro'd that would work well there.
I like your circuit... nice and simple. I've heard tales of the 27 being a bit microphonic and not the quietest tubes. But nice stuff.
MSL