Haystacks rhymes with:
smokestacks, aftertax, counterattacks, macintax, overtax, pentax, smokestacks, surtax, syntax, turbotax
Haystacks sounds like:
hajduk, hasidic, haystack, hecht's, hectic, hegedus, heights, hesitates, hightech, hoechst's, hoists, host's, hostage, hostages, hostages', hostess, hostesses, hosts, houseguests, huestis, hyakutake