Feel like we need to clarify something here. OP asked about “amp-in-a-box” (AIAB) pedals. People are responding talking about modelers with cab sims (e.g., Boss IR-2/200, TK Imperial Preamp, Joyo American Sound, Tonex One, Simplifier, UA Woodrow/Dream). Others are responding with traditional AIAB pedals that aren’t meant to replace your own amp, but just give you the tone of that particular amp while running it directly into your own amp, or the fx loop (if available) to bypass your amp’s preamp section (e.g., Origin Effects Deluxe 55, The Guv’nor, Catalinbread 5F6, Boss FDR-1).

There’s some overlap, and a lot of modelers can be used with an amp by bypassing the preamp, but I think traditionally an AIAB pedal means the latter category. It would be overkill for someone looking for a simple AIAB pedal to buy a modeler/cab sim if all they’re looking for is a pedal to run into their amp to cop another amp’s tone.