Actually though.....
I HAVE used non-professional quality SVHS tapes in ADAT's before. They will work, but, Alesis does not recommend them because generally the consumer quality tapes tend to wear out really fast, which could cause some significant damage to the tape heads.
This would only happen if you were using the tapes heavily, like you would during a CD production. But if you just need to archieve, or run a lot of tape for a session, then maybe transfer the tracks to want to better tapes afterwards, the consumer quality one's will hold up long enough to do that for you.
Anyway, I just would never commit any music that I care about to cheaper tapes. Quantegy is just the old Ampex brand, which I have had the most problems with. I have talked to other engineers who have had many problems with Ampex/Qauntegy tapes too, so be wary of heavy use. In fact, the only time I ever had a tape break on me inside an ADAT was an Ampex tape. Also, I don't have ANY drop out problems with the Maxell's, but many with the Ampex tapes.
The Maxell's are the best.
Ed