I found the perfect bag for my Walkabout head and thought I'd share: Gigskinz make these as mobile recording rig bags (model GSMR), but it's perfect for a small head (like a Walkabout). I fit my head, mics, and cables in this with plenty of room for extra goodies (like earplugs). It's even got straps for both shoulders, so I can carry this on my back like a backpack and still have both hands free to cart my cab. I think they go for around $60 at Ye Olde Guitar Centere. Highly recommended.
I have the small one for my Eden WTX-260. Great bag! I liked it so much I bought the gig bag for my bass. It has great storage and a nice interior-furry like the mixer bag. I highly recommend them both.
Yep--great bags. I use one with my WT330 and WT400. The medium bag is the perfect size for those heads--fits like a glove.
I got very lucky with my Markbass F1. It actually JUST fits in all 3 of my gig bags as well as the front pouch of my Pedaltrain pedalboard softcase. I was about to buy one of those and would have if my amp was too big for my cases.
Stacked on top, or side by side? I'd worry about them shifting inside the bag, though, and scratching each other up.