Here is what seem to be the best modelers today (no particular order):
Kemper Profiling Amplifier
Fractal Audio Axe-FX
Line6 Helix
Amplifire
All are essentially DSP-based, using algorithms which mimic amps based on their circuit schematic -- except for the Kemper which models the amp as a black-box at a higher conceptual level. All also use Impulse Response (IR) convolution to reproduce the speaker cabinet response.
Kemper Profiling Amplifier
Fractal Audio Axe-FX
Line6 Helix
Amplifire
All are essentially DSP-based, using algorithms which mimic amps based on their circuit schematic -- except for the Kemper which models the amp as a black-box at a higher conceptual level. All also use Impulse Response (IR) convolution to reproduce the speaker cabinet response.