I use an Ashdown CTM-300 all-tube amp. Boasting six KT-88 power tubes and five preamp tubes, it's a true 300 watt beast. I discovered this amp through Jason Isbell's bass player, Jimbo Hart, and I fell in love with the tone. Overall, the EQ options are pretty subtle, but that's what I love about it. I can get a wonderful, organic Americana rock, rootsy country tone no problem, and if I want to get a little more punk I can crank the gain and crunch those tubes.
I tried the Orange, Ampeg SVT and Fender Bassman heads prior to settling on this head. Those are all great amps, but Ashdown just happened to be the one for me.
Only downsides are the weight (75 lbs or so) and the light in the VU meter burned out relatively quick (VU meter still works).