I use a Klystron 100 head with two classic neo 4x10's, been regularly giiging with them for about 4 years now. Absolutely no problems at all, get the head serviced every 6 months. Definately the best rig I've ever had, just run the eq fairly flat with just a touch of mid boost and it sounds awesome. Dont boost any of the bottom end or it can become a bit boomy. Ran it side by side with a Mesa M9 carbine head and two powerhouse cabs and the ashdown blew it away.