All the biggies produce A3/A3+ printers.
Canon i9100 is supposed to be brilliant.
Epson do a couple they are supposed to be good.
HP also don't want to be left out.
So you pays yer money and takes yer choice.
Have a look click here it has reviews on most of them.
Am waiting for Canon to turn the i965 into an A3/A3+ then I will dive in and buy one myself.