There are many ways to get the sound you desire. You've already received a lot of good advice. From my experience, if you are going to start stacking guitars (doing more than a double) they better be extremely tight. You have to take great care with each track and make sure that rythms are dead on. The second thing is that the amp matters a ton! You should look at Mesa Rectifiers, Marshall JCM 2000s, the DSL, not the TSL, and many of the Randall MTS modules can be totally amazing. Third, use a guitar with humbuckers, especailly Les Pauls and SGs and others like a really nice Iceman or something. 4th as far as mic positions and mic choices go do what ever you have to do to get amazing midrange. Most of these amps are dangerously powerful in the low end and in the sizzle. Too much of either of these, especially the sizzle will kill your guitars in the mix. I get a lot of distorted guitar tracks to mix that sound like a guitar mixed with someone blowing a hair dryer in your ear. Those big guitars you like live in the midrange they have to be awesome from 150hz to 2-3k. Almost everytime I'm tracking a Les Paul Mesa Rectifier set up, it usually looks something like the following (always adjust for the song and the part and the player).
Les Paul treble pickup>Mesa Rectifier> Modern setting with solid state rectifier and the bold setting, Master at about 9 o'clock, presence at about 10 o'clock, bass at about noon, mids about all up, treble around 1 o'clock, gain at about 1 o'clock. Going into a Marshall Cab with 25 watt greenbacks (careful you can easily blow these speakers with setup, I usually set the volume as loud as I can to the point where the speakers are on the edge of being pushed too much, its actually not that loud. These speakers have the aggressive mids that you want.) I usually start with a 57 about two inches away from the grill cloth pointed right where the dust cap meets the cone. I also use another close mic like a 409, 609, u87 or u47 up close. I take great care to make sure that they are totally phase aligned down to the sample. I also always record a room mic that is sometimes used in the mix. I'll record one set of tracks panned hard left, with the room mic hard right, and one set of tracks hard right with the room mic panned left. I often use a different high gain amp for each side, as well as a different guitar for each side. Whammo huge sound.
Sometimes I add third and fourth doubles for key moments. But only a little. I hope this helps. For a really simple song example that uses this technique, check out this band. These are not quite final mixes, we're in the middle of making this record.
www.myspace.com/linusrock Check out "Time to Go" and "Red".
Hope this helps.