The E34L's have a little tighter low end than the standard EL34's, they are also a bit punchier and agresssive than the standard EL34. I have a set I was using I like the way they sound, they bring a little low end back in to your sound. You just have to be careful cause they run hotter, which means they may die a little sooner. I was using them in my dual rec with good results, I was just warned to use the tube mode, not the diode cause they won't have a very long lifespan. If you want to find out more check out this site...
http://eurotubes.com/euro-e.htm
http://eurotubes.com/
It gives you descriptions of different tubes, if you want to email them any questions they are good to respond.