I would consider
THIS one, which is just a bit over your budget. I've got the non-belt-drive close equivalent (Verge S11i) which is now 9 years old with over 10,000 miles on it. There's probably a premium on the S8i because it is a folder, which is a feature you may not need. I've been very happy with mine in routine commuter use; I've done a couple Centuries on it as well.