At ~$9 a tube, the EH is priced right. I find them toward the yin side of neutral while lacking the depth of tonality I hear in a nice '40's RCA 6SN7GT. They are not as etchy, ringy, and bright as the Chinese varieties I've tried. The EH neither sheds any particular magical light nor grossly offends. If you've only one 6SN7 to buy, why not spring for several used NOS types like you mention and find out what you like - it should be fun. I'll second Andy at Vintage Tube Services as a great person to talk to about that 6SN7 in your preamp.
Here is a link I find helpful: THE 6SN7 ARCHIVE THREAD
Cheers,
Tim
Here is a link I find helpful: THE 6SN7 ARCHIVE THREAD
Cheers,
Tim