This is the route I take but doesn't go via Devil's Bridge. Nice scenery and some good roads though.
A466 to Monmouth
B4223 to Abergavenny
A40 Across Brecon to Llandovery (West End Cafe)
Then I pick up the A482 to Aberaeron
Then nice ride up A487 to Machnylleth
Chips at the Dolphin in Barmouth, Happy Days