try a CAD Trion 7000 ribbon mic. I really like it- I put them both up close though. The CAD gives you warmth and fatness.
Fatter and tighter may be a cabinet or amp or guitar problem. Make sure those are decent first. Usually a 57 in the right spot will do the job...
It sounds perfect in front of me.. just doesn't translate the same on the recording.
It might be a question of using the right mic for your amp.
The SM57 has been an industry standard for years but in my experience not all mics are suited for all amps.
Several years ago I had a Custom Vibrolux. I tried a 57 to run it through the PA but it sounded awful, too much presence and very nasal. I swapped it for an ancient AKG and the amps true tone came through.
Later I tried the same 57 on a Classic 50, 2x12 and it worked beautifully.
So, don't place the mic as close if it sounds better when you back it away from the amp a little.
I'm not trying to be an ass but it seems as if you've found a sweet spot for the mic while recording that amp. Why not use it?
In front of you?
Bend down and put your ear as close to the speaker as the mic is, how does that sound?