I'm a drummer and not an electric guitar player but after many years of playing and recording with top notch guitarists I have payed attention to the "what amp will give me the best tone/distortion" dilema. From my observation, I'd have to say the Mesa Boogie amps would be hard to beat in both tone and quality. They are the only amps I've seen really hold up during the rigors of touring and the tone available from these amps speak for themselves. Also, I noticed once players get a Boogie they stop searching for another amp (and I've seen many go through 3 or 4 amps in a year searching for that "sound" they've heard or want).
However, a lot of new/young players don't spend the time to really learn how to get the most from these or other guitar amps. They sometimes become frustrated because they don't immediately get the sound they want. Small changes to settings on Boogie amps can make significant differences in tonal characteristics and the complexity of these amps require some time and study to allow you to get what you're looking for. In my humble opinion, too many players look to outboard gear too soon to get the sound they want. Learn your amp inside and out first, then add what you feel you need to embelish. I've watched the pros in the studio make these amps produce incredible sounds of every kind with very little outboard gear by turning a few knobs on the amp. I've also seen the results when players really spend the time with their Boogie and learn how to make it produce. Some of the most toneful and varied live sounds I've ever heard have come from nothing more that a Boogie and a pedal (admittedly I had to ask to find out the truth). The tone is there but it takes time to learn how to master it and when you do you'll be a better player and separate yourself from the crowd.
One of my sons spent some years on the road as a sound engineer and he claims the Boogie equipment to be far more reliable than anything he had to deal with. But what about tone? Well, he had an interesting story about a very recognizeable band he mixed. They removed the name plates and camoflouged the amps and speakers so you couldn't tell they were Boogies. They were upset at Mesa because they wouldn't give them the amps for free (they give NO ONE free or discounted gear, even this big name group). They were also sponsored by another well known amp manufacture who supplied at least some of them with free gear. The guitar players weren't about to sacrifice the tone they prefered from the Boogie amps so they forked out the cash anyway (and of course complained about having to do so). I think that pretty much speaks for itself.
In our studio we keep
Mesa Boogie Mark IV and
the Bass 400 amps on hand. One tehnique that can be helful for guitar is to have a variety of single speaker Boogie (or other) cabs with different speakers. This will allow you to experiment and shape the sound depending on the need. You can mike multiple cabs and A/B or mix them together, just keep them isolated from each other to avoid bleed. This can really make a difference in your pre-EQ recorded material so you might want to audition some different cab/speaker combinations to see if it gives you what you're looking for. Same technique can be used for live gigs.
Ultimately though, your ears should make the final choice and there ARE other great amps available so spend the time to audition everything you find interesting. I realize Boogie amps are expensive and that can be a factor for many players but that's a decision you'll have to make. Hope this is helpful, good luck.
Dennis