I've had ecellent results recording the SansAmp products and a variation of the Roland COSM modeler.
See my other extensive post below about the SansAmps (emulators, not modelers) and the POD.
Regarding the COSM, I've used the amp modelers on my VS-880 for years and have gotten great results. These amps did a great job for cleaner tones, but were a little lacking in the distortion department. However, after driving the signal a bit at the input with an external preamp (i.e., TubeScreamer or GT2), the distortion began producing quality tones with excellent sustain. The amp began reacting with subtle harmonics and feedback like it was driving its power amp into pleasant distortion.
Similar results might be obtained from their Boss line that uses COSM, but I've never tried it. Also, the VG-88 has good clean tones, but also lacks in distortion. Unfortunately, the VG-88 uses a digital input from a MIDI-style pickup, and therefore cannot be overdriven by an external preamp.
Me