Honestly it'd be expensive even used brembos. You're factoring in shipping, pads, line fluid for the akebonos on Z1 and saying it's 3k. Fair, but if you picked up used brembos, they'd be at least 3k for a full set, and then you still have to pay for shipping on those, plus fluid plus pads and then as you indicated, new rotors. The new akebonos will more likely always be cheaper than a brembo kit, even if it's used.
It really comes down to what you want out of your car (DD vs. tracking).
I read in another thread you started that you totaled your 350 on black ice and I noticed you live in Canada (
anyone here DRIVE there Z in WINTER?). If you're going for new brakes to avoid another accident as opposed to performance I'd say go with the cheaper option (akebonos) and more importantly, get a good set of winter tires if you haven't already. But honestly if you're worried about another accident it's more to do with driving than anything else, and honestly a set of bigger brakes won't do too much.
edit: last used brembo kit I've seen on the370z, asking was $5350
***One Of A Kind*** 2009 Nissan GTR Brembo BBK