A while back I acquired 2 x 24-gun Buffalo River cabinets, and keep one for rifles/moderators/optics and the other for shotguns/rifle ammo/bolts. I'd estimate the shotgun capacity as about 18 and the rifle capacity as about 14, but there's a good amount of incidental space for other bits and bobs. The combination locks are a bit battery-hungry and occasionally temperamental, and the safes can't boast the fire-retarding capability of more expensive equivalents, but overall I'm happy with them. Access is much quicker, and the guns much less prone to "safe rash" than with my previous series of small, single-figure safes. Total cost was about £1,300. If buying again today, I'd probably look for something a bit more up-market, even though I probably don't actually need more quality than the Buffalo Rivers already offer.
On the rifle side I recently got some extended foam inserts (from Brattonsound) that support big scoped rifles better than the standard racks. Also useful are the velcro-tipped rods (from Brownells) that you drop in from the muzzle end and then lift and stick to the carpeted "ceiling" of the cabinet, since they let you store rifles in the centre of the space, -or for really short ones, under the shelves- as well as at the sides. Another benefit of the extra space in the larger cabinets is that there's room to put in motion-sensor-activated LED strip lights, which make it much easier to see what you're doing and to find what you're looking for.