What I have found is that it's almost impossible to compare tubes because of the time it takes to swap them and let them warm up. But so far, with only a couple of hours of play/listening, I can't tell the difference between the GEC, my CBS Hytron 6AS7G, or the original 6080 that came with my Crack. I will say the GEC is significantly better than the 6080 in microphonics though (and equal to the CBS Hytron).
I'll give it more time, but my first impression is that either the GEC is highly over-rated or the CBS Hytron is an undiscovered gem.
BTW, today is the first day I have listened to music in over 2 weeks due to travel and ear fatigue. I've been listening to k.d. Lang "Ingenue" and man oh man thie Crack/HD800 sounds so sweet. One of the best combinations Ive ever heard. To be cliche, it really is just a musical, fun, organic sound quality. I really can't imagine the Speedball (or anything else) improving it.