Yes, you'll need 16 channels to go between the Otari and your board.
I'm sorry dinty had a bad experience with the M-216, but my experience with a neglected M-308B was quite the opposite. Best sleeper deal in small format mixers IMHO is the M-300 series.
If you DO get an M-300 you'll need TS jacks for the mixer outs (if using the DIRECT OUTs) or RCA's for the mixer outs (if using the BUSS OUTs) and RCA's for the tape returns if you want to use the TAPE inputs.
The 2500-series is also really cool...carries on the tradition of smart and plentiful features and good sound. You'll need RCA's for the BUSS OUTs on the 2516 and RCA's also for the TAPE returns. The upside of the 2516 is that it is an 8-buss mixer as opposed to the M-300 series which are 4 buss, so you'd be using the channel direct outs and repatching as needed on an M-300 or just using the 4 busses and only recording up to 4 tracks at a time. Having 8 busses is not essential for an 8-track recorder, but it is a really nice function to have infinitely variable patching and grouping at the control surface of the mixer.
[EDIT]
Don't forget that your Otari is unbalanced.