I know I've said it before, but....

[NAD613]

Those Akai SX type I cassettes may be the best type I tapes I've ever used. I don't know if I've ever heard a normal bias tape with as much high end as those tapes. Maybe it's because I record them with the bias at around -1.5. I'm listening to one right now & the sound is fantastic! Maybe the best bargain of all time.

[Des-Lab]

I have some on order and will definitely post a full test report once I have a chance to evaluate them. So far, based on what you are saying, they sound very promising.