I have that basic model as well, always found it to be a pretty good tape deck. I can't remember for sure what I have without checking, either the 630ES or the 615ES. Dolby B, C, S, HX Pro, manual bias adjust and calibration, 2 motor I think, 3 head -- definitely a solid deck. Use the RCA outs for sure, not the headphone out.
BTW, 3 head = 1 erase head, 1 record head, 1 playback head. As opposed to 2-head deck with an erase head and a combined rec/play head. Having separate record and playback heads allows you to monitor thru the playback head exactly what was put onto the tape from the record head during recording in realtime. As opposed to recording the tape and then needing to finish, rewind, and playback to see what you got.