Sold PS3 console on ebay

hi i've sold a lot of small items on ebay before, but today i sold a used PS3 console to someone in Belfast. I have always used An Post in the past but is this the cheapest way of sending an item of this size or is there a cheaper option? I've felt like i have been overcharged by them in the past on much smaller items and am a bit wary of using them for a package so big.

Also can i bring the console to my local post office or would i need to bring it to the GPO since the package (boxed PS3 console) will be big? doubt it would fit through the hatch in the smaller places.

Thanks for any help