Congrats on the M4 and NS-1000s!!! I have a M4 that i got from a guy who at a party someone spilled a beer on the left channel amp boards and supposedly it wouldn't work so i got it for a song. Well ended up it needed new trim pots and i went ahead and recapped it and it sounds great!!
BTW, from what Dave (avionic) has said, don't use Deoxit D5 on the volume pots in the M4. Use D100 because the D5 will desolve the carbon traces in the M4 volume pots.
Thanks for the recommendation - was going to use Deoxit-5