There are those moments you love to use a small amp during your gig or rehearsal. Smaller amp may sometimes be more practical, or maybe a particular amp does have a sound you would like to use.
Smaller amps do not have the body bigger amps have. In the context of bass and drums they may loose their presence and character. Use them in the context of a larger P.A and monitor speakers and there may not be such a problem.
All of this will depend on the band set-up: If you are playing with another guitarplayer and this person uses a much bigger amp, you may find yourself competing on the volume level.

If you are the only guitarplayer you may get away with it: Use the monitorspeakers as part of your amp: Get your guitarsound coming from the monitor as well, try to blend in the level of the monitor with the level of your guitar amp. Once you have the right level you may like the sound, and it may be big enough for the band to work with.

Once your guitarlevel comes through the main P.A the levels can be set in such a way that noone will notice that you are playing through a small amp. Needless to say that you will need to match your level with the rest of the band, once that is in place your guitarsignal can go anywhere.

Happy Playing.
See you soon again,
Eddie