When I was a recording arts student 10 yrs ago, the go-to studio tapes were Ampex. It appears they (either the tape div, or the whole company) was sold to a 'Quantegy'. Ampex 456 Grand Master was *the studio tape. I see they (Ampex by Quantegy) have 7" reels for around $10. I would certainly audition the current product.
You gotta love the metal reels; no cheepshit plastic stuff...
Ampex Grand Master cassette tapes were another story. They sounded great, but IME, they had a longevity prob. After many years, say over 12, a rewind would snap the tape off the takeup reel. Grrr... But then again, I wouldn't consider the tape cassette an 'archival' medium. Kinda like 3.5" floppies are turning out to be...