Sherod,
Thats the exact same application I first heard them in.. A Tube Pre output cap, 1 uF stereo pair. Excellent from day one, trounced the Auricaps originally in the unit, and all that followed, the Jantzens, the top line Mundorfs etc... Nothing wrong with them, and the bass(low frequency) foundation of these in a full range application like that is just scary!
I have sinced put them in for a friend similar application, same excellent results, and re-fitted a cheap MC phono stage with them that made it go from a 300 dollar sounding unit to a 5000 dollar sounding unit! I mean in a phono and simple tube preamp there is not much else there accept the absolute quality of the tube and caps, so you can really work wonders with these simple designs.