I'd prefer at least a couple that are either from a combi or a pump. Better shower experience and less risk of big cables and overheating isolators etc.
Stick the two 4 ohm speakers in series and you won't damage your amp. Won't be hifi quality due to the more restrictive bandwidth of a guitar amp, but still may sound OK.
Or if the amp really is 2 x 4 ohm then connect one speaker per output.
The 4017 can do a 10 LED chaser on its own. You use daisy chain more than one 4017 together by connecting the last output of the 1st IC to feed the clock input of the 2nd.
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