Each week I get to listen to some excellent guitar work mic'd into a sound system that is probably the best on the entire Gulf Coast of Florida.
The guitar player recently acquired a VOC AC 50 to play through with a Tele. Mic'd with a Sure SM57 it sounded quite good. This was the set up for a few weeks before going "direct" out of the back of the VOX using it's built in modeling. Very nice! Yes, I said it. It sounded considerably better than putting the mic in front of it. More punch, and more of what sounded like a "genuine" Vox jangle and grit. I didn't even know the switch had been made until I complimented the player and dialing in the sound.
Then about a month later, WOW! His rig sounded incredible. The best guitar tone that room had seen. The change? You guessed it. He had switched to a Pod x3 Live and downloaded patches from Lincoln Brewster. He had the Vox still sitting on stage so I thought he was still using it.
I won't say it sounded like a VOX. That may be Brewster's patch work. But it sounded good! Real good! And that seems to be my experience listing to the last two generations of Pods when played through PA or recorded by a talented guitar player. They always have a great tone even if when they don't necessarily sound "just like" an identifiable amp/cab.
I know a lot of Pod veterans hate the Pod x3, but that may be because they are trying to use it like a stomp box...plugged into a guitar amp. Reading the reviews on Line 6's site it seems the ones most dissatisfied with the Pod x3 are those plugging into an amp. "Digital hash....gritty...etc." It could be the x3 is more live and revealing, and that puts it at a disadvantaged when used with many guitar amps. Why?
I repeat, no Amp Modeler was ever really built for the purpose of being plugged into a guitar amp. They were designed to be plugged into "nice" neutral and accurate rigs like a PA or a recorder.
Studio speakers and guitar amps are vastly different. Studio monitors try to recreate accurate tone at the expense of dynamic punch and durability. This is essential if a recording engineer is to lay down tracks that best reflect the performance. But Guitar Amps like my Mesa Boogie Simulclass 2 90 and Extension Cab are built to be LOUD and kick hard all day long without breaking. Example: in my studio I can get my monitors very loud (120 dbl) but the instant I first fired up my Boogie rig it knocked a painting off the wall. And yet the "watts" in both systems are the same. But my B & W monitors just aren't built for that type of punch.
PA systems are built to be loud, but again, to be "accurate" as possible. Volume is gained by redundancy, adding more and more and more amp and speakers components that fan out to fill the venue. Like a vast array of flood lights. By contrast, a big rig guitar amp is like a single one million foot candle spot light. It will take your head off if you're right in front of it and close. But get 100 feet away on a stage outdoors and it's fallen off to a whimper as far as punch goes. Yeah, it can still pierce your ears, but it won't slap your chest. It can't send enough bass and low mid that distance outdoors to "feel" it. But you can still hear the effects of that slap on the amp cabinet speaker surrounds. Those artifacts (acoustic distortions) are in the mid and high range. And a good modeler captures that, just like a mic would in a PA system.
But running a guitar amp modeler into a guitar amp? That's kind of like having two NFL teams suit up, take to the field, then sit down behind Madden 2009 to compete with each other. Oh sure, you can do it and sometimes it sounds good once you "dial in" the right sound. An it might be fun to play. But a Fender Deluxe won't sound like a Marshall JCM 800 any more than the Detroit Lions are going to become the New England Patriots because they sit down at Madden and set up a Patriot team on the Xbox 360. They might have fun (clearly the case with Detroit...much more fun that their football outings of late), but it won't be what was intended, or be the Pats.