The Crossgen stuff and a lot of publishers like them actually have very good reads, and some of them have very rare variant covers. A lot of the titles you already mentioned: Halloween, Chaos comics....also a lot of the B-C list bad girl comics have niche but collectible markets. I think you should pull them out by title and go through them, 1500 comics isn't a ton!
Sight unseen it was a no lose buy....a few years back I bought 11 shorts for about $500 because it had a good run of Spawn. The rest of the stuff was easy to sell at $50 a short - low risk venture. You could easily do this with this lot, dump some of the longs in the $40-50 range.
Also look out for newsstands of all the publishers. I actually probably prefer this type of collection buy over any other because it's not much work at all, little to no monetary risk, and you'll educate yourself on a ton of titles that you never knew of for the next time. EG Maybe there's a bunch of Avatar comics in there with value that you never heard of before.