This is a great campsite, right on the doorstep of Coed-y-Brenin: Cae Gywn Farm[/url].
Makes a good base for CyB, Penmachno, Antur Stiniog, Cadair Idris etc, then you can go south via Machynlleth, Nant yr Arian, Brechfa, Afan and so on… You’ll have to be selective, there is too much to ride in 3-4 days.
I did a similar trip a few years ago, but the other way around. We did a whole day at Afan, Nant-yr-Arian the next, on the way to Cae Gywn Farm, whole day at CyB the next day, Penmachno then home on the fourth day.