i was training for 1500/3000 this winter, running workouts like 6x600m in 1:38 with 90seconds rest. nowhere near 60 second quarter pace but when called upon to race in the 4x800 at bigger meets I went ~1:58 twice. Granted these weren't open 800's but i was never timed slower than 1:58 and was timed by multiple teammates. i guess my point is you don't have to have insane speed to go sub 2 and it would seem having a very solid base with a little natural speed can get you there just fine. 400's in 58 or 200's in 27 aren't the only way.