As far as reliability goes, and the A3 part, I would suggest that you look into a second hand HP8500DN or something similar. They're large and clunky, and the consumables aren't the cheapest, but they're quite fast and last forever. They'll do duplex as well, and you can pick them up for fairly small amounts of money. Multi-sheet feeder bins are available, and all sort of accessories.

Most of the older HP industrial lasers are a much better buy if you're going to print more than a small amount. They're designed for pretty much continuous use. I have an 8000DN which is the mono version of the same one, and it has given me 3 paper jams in the last eight years, and gone through at least 15k sheets in that time. Which is a small fraction of the usage it's rated for per month. With the 2000 sheet feeder it cost me less than £100 GBP, and toner cartridges are cheap.

pca