Now, I personally like a head better, but some rack units can be quite awesome. Originally I had a Rocktron Voodoo Valve paired with a Mesa Simul Class 2:90 and that is a pretty nice combo. The tubes in the Mesa gave the Rocktron more warmth, more volume, and a less digital sound. I particularly like that pairing for soloing. Now however, I love playing through my head, it is a Hughes & Kettner Triamp MKII. I just feel like it is more alive and responsive than any of the rack units I have played through and many other heads even. While it is expensive and fragile as well, it has a big sound that cuts and is also really warm and smooth sounding. Those characteristics, along with 3 different channels that each have an A and B, have given me exactly what I want in an amp for the last 3 years. My other guitarist is playing a Mesa Tri-Axis through a 2:90 and that is sounding pretty cool as well, but I personally feel like Mesa's kind of have a somewhat cold and dark sound. Although, definitely warmer and fatter to my ears than a non tube amp. So, I guess it's all in "ears" of the beholder.