what would be the best speaker cable under 1k used or new to used with the 3.6 maggies

Length need?  Prices can vary significantly...

op

really depends what tonality or subtle shaping of the sound you presently hear is being targeted

anyone blurting out their favorite cable isn’t really answering your question for your application

you also need to disclose your current cabling

taking into account your notes on the above, replies may be more useful to you

I don't know about best, but the Clear Day Double Shotgun is good with Maggies. It retailed for $500/8 ft. pair when available, but is now out-of-production. Patience is required!