I have Ashdown ABM210 and mini48 cabs and I just sold my Shuttle 6.0 (waiting delivery on the 9.0) and this will be a good match.
The GB Shuttle 6.0 is a great head and will work with anything. I've used it with Aguilar, Ampeg, Ashdown, GK, Eden, Trace-Elliott, etc...and it was fine. You can always use the eq to correct if something is missing or over the top on the cabinet.
The ashdown ABM cabs are fine in general. Nothing really special but they get the job done.
If your friend has a cab from the MAG serie, those are not so good but hey, you won't have to pay to use it?
I'd not recommend to purchase a MAG cabinet. They are cheap but sound cheap too...IMO.