... and, BTW, this is *not* a stupid question.

Very few manufacturers actually specify the degree of 4 ohm support these days (for legal reasons as far as we know, not technical ones) so the only way to find out for sure is to either buy & try or ask other people who might have experience with a particular receiver.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8