Walls of text go unnoticed so PM me if you want more.
TL15 or TL30 on CL, TL15x6 or TL30x6 is better because x6 indicates all sides are same strength as door essentially. You can't do the sardine can peel on one of these. Which is, btw, the easiest way into an RSC which has a 5 min. rating against short hand tools and one attacker only. TL15 will withstand 15min. attack 2 guys 200lb. w/long handled tools and power tools of their choice. TL30 is 30 min.
All of them usually have a better fire rating than a typical gunsafe or RSC, but if you get an older one or a used one you may want to go buy a palusol (sp?) seal that goes around the door. It's just a thick "gasket" thing that expands if it gets hot. Older ones didn't come with 'em.
Look on CL, be patient. One time an 8' Mosler bank vault from an old bank showed up and it was $4k --but I didn't have a place to put it (and it would've cost at least $4k to move that!). Every now and again one will pop up on there that fits the bill, but most are smaller 4.5 or 5 foot TL15's or TL30's (great if you need a second one for parts, handguns, SBR's, whatever, but you can't stand anything up in one that's longer than a collapsed M4 IIRC). Those are most common BTW.
Look for a large safe dealer, they sell volume and have scratch and dent new stuff, used stuff, you name it. All sizes and they know how to move 'em. Remember that these types of safes start around 1200lbs for a "small" TL30 and more like 6000lbs. for full size TL30x6. I'd go for the TL30x6 if you can, vet discount, scratch dent, used --pour it on and negotiate their bottom price. A lot of times they get the used ones for a song, or get 'em broken or locked and repair them.
IMO, Original is the brand you want. There may be better but I don't know of it short of a Diebold or Mosler. You can get 'em with dual locks, combo and key (I'd go dial combo and stay away from the keypad shit were I you!). The TL30x6, their biggest one, is the one that's on par size-wise with most gunsafes. Unless you're collection is massive or takes up a ton of space, this will hold it all.
Best way to go IMO is to get the big TL30x6 from large dealer for a good price (used, scratch and dent, whatever) and a smaller used basic TL30 or TL15 on CL.
Shit, still went on longer than I intended. Sorry.