I wouldn't mind having a 1550 myself, however, the 1600/1650/1655 tractors are very much the same size with a few more ponies under the hood. However, the 4 digit series are of the same mold. While you wouldn't need the HP of something much larger, I wouldn't pass on a 1750 or 1800/1850 if the price was right. 

We hay with a 1800 series B with the hydra-power and a 1650 (both gas). 

Our 1650 is not a hydra-power tractor. It is primarily used on the rake and for bush-hogging. We tried it on the baler, and it does just fine. However, having used both, I do recommend the hydra-power or one with the over-direct-under option. 

Only drawback I've found with our 1650 is with the steering, if the tractor isn't running, your not going to steer as there isn't a physical connection to the gear (all done with hyrdaulics) like there is on our 1800. 

I hope you find one. You won't be disappointed with any of the Oliver choices in the 4 digit series.