How to get started with loop pedal for rhythm and harmonies?

[redpoint]

I'd like to get started doing looping with my acoustic at home, mainly to loop rhythms for solos, but also to do harmonies with msyelf, but not sure what to get.

I need a loop pedal (RC-20XL?), but to hear the looped acoustic, can I use an electric guitar amp (have a Vox 4W) or powered monitors? Or do I need a real acoustic amp? This setup takes care of the rhythm part, but how do I also sing harmony with myself? What's the setup for that look like?

Thanks!