I have an amp/record player and 4 speakers in one room, I would like to add 2 speakers in adjoining room ā so the amp ideally would have 6 speaker places (my current amp has room for 2 speakers, but I have put extra wires in each one).
You shouldnt do that. It (approximately) halves the impedance amongst other problems.
What you end up with is the amp doing twice as much work as it was designed to. A 100w amp plugged into a 200w speaker only produces 100w of power, a 100w amp plugged into two 100w speakers in parallel produces 200w, which if cant so it goes pop (or distorts horribly).
If you get 4x pairs of speakers you can Daisy chain them (wire them as a 2Ć2 grid with two in series and two in parallel) and itāll work, but it always has to be a square number (1, 4, 9, 16 pairs), and the speakers should be identical.
You would be better off buying a propper multi room amp, or a distribution amplifier (which takes one line level input from your pre-amp and splits it into as many outputs as you need) and putting separate amps in each room.