I would sugest that an A4 printer would be your best option if you are going to be printing a lot as there will be times where you maybe want something bigger than a very small 6x4 print. the Epson ET-2781 is on offer now at Epson's own website, but a cheaper option would be the ET-2862. These would offer good quality colour prints on a range of photos papers with very reasonable running costs.
I've got a Canon A3 pigment ink printer which produces stunning results up to A3+ size on variety of different papers, but the running costs are much higher (£150 for a set of ten inks)