For the electric tones on my P22, it's hard to beat mic'ing an amplifier. When I can't do that, for just "scratchpad" tones, I use my old POD XT, although I am looking to upgrade it to a Fractal AX8 in the near future. On the rare occasion that I decide to use an amp sim plugin, an active direct box will do the best, although you can get by with passive in a pinch. Does your audio interface have a Hi-Z instrument input? That will work in lieu of a direct box if you have one. I occasionally use Guitar Rig or a couple other amp sim plugins in my Windows based recording rig.
For the piezo acoustic tones, I have an older Zoom A2 acoustic modeling processor and a TC Electronic Bodyrez pedal that I use together to make the tone sound a bit more natural, but I only use the piezo for scratch tracks or special effects. I have not found a piezo sound yet that I would want to keep as an acoustic guitar track compared to using a decent microphone on an acoustic guitar. Even a cheap acoustic (as long as it's in tune) will sound better recorded with a microphone than the piezo signal from a lightly strung solidbody - in my opinion. I have heard a couple of guitarists get really good results using the impulse modeling (or whatever that feature is called) in a Fractal AxeFX II, Alex Lifeson and Eric Gillette (of the Neal Morse Band), but we're talking very high dollar gear.
Now, for playing with a band and having the versatility to switch tones mid song, the P22 can't be beat, I absolutely love mine - you just have to know its' limitations.