dont worry too much about spring rates. what you feel in a rough ride is the dampers, not the springs. i have 11/7 springs over bilsteins (custom setup) and it rides quite a bit betterr than any other coilovers ive been on.
for your budget i'd say stance's from rishie (AutoRnD). they're the best riding off-the-shelf budget coilovers ive experianced so far. wayy better than megan/ksport/cusco
also, buying used suspension is a bad idea. you never know if a shock is gonna be blown. most ppl dont even know how to tell.
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