[vcf-midatlantic] (off topic) - options for smaller than 19" receiver/amp for multiple RCA connections?

Hey folks, Just wondering - I have multiple vintage devices sharing an old 19" Onkyo receiver. It works great but takes up a lot of desk space. If I replaced it with a smaller amp (that I could mount under a desk) what are some options for hooking up multiple RCA cables and switching between them? Would appreciate links to example devices. (Fwiw - currently I keep an Amiga, an ST, and a Sega Genesis attached but only use sound on one at a time. May add a 4th device later). If you're linking something with an amp (which is cool) my power requirements aren't huge. 40w RMS would be ideal. Thanks! John