I tried a few cabs with it tonight and liked it with a couple of the newer 4x12 mix cabs (the Dumble EV12 ones in particular)...interesting amp...got a cool 70's Stones tone out of it. Lots of color/variation playing with just the Drive and Master. Definitely going to play with it more...
I have played a Carr Rambler for years and love that amp to death - asked for it in the wish list threads.
The mid control is very responsive and important to get all the shades out of the Rambler - be sure to check it out.
If you back off the mids it will take a on a very sweet Fender Black Face personality, sort of a Deluxe but with a bigger bottom end and more warmth.
Push the mids and the volume and it'll take on an almost Tweed Deluxe personality.
In the Rambler model in the Axe you can do so much more, and I have found some cool sounds with the mids pushed and the fat switch on.
Regarding cabinets, I found that many of the 112, 210 and 212 Fender cabs (cabs roughly 80-90 or there about IIRC) works really well.
I had great results with the Tweed Deluxe mix, PrinceTone 10" Silver and Vibrato 12".
For non-fender cab sims I found the Nuclear Mix, Scumtone and EVL IR's really great.
Kevin from OwnHammer will be releasing a 112 and a 212 open back cab pack (very) soon, and these will among others have IR's of a J12 PR, a Fane and a EV-SRO - I've found that these worked exceptionally well with the Rambler.
I only had 90 minutes or so total to play and test IR's with the Rambler sim, so there's lots more to try out and tinker with - but I already really love it.
When I get my Rambler back from a friend who loaned it for a studio project, I'll put them head to head and see how well Cliff nailed it.