My experience has been some amps are easy to bias some are not so easy. Check the instructions on how to bias the amp before buying anything. Personally I like to set the bias if the process is reasonably easy.
Manual vs. Auto Bias
In considering new directions in which to take the evolution of my system, I have run into conflicting claims as to which results in less distortion...auto or manual biasing, according to what product(s) the so called expert manufactures and/or represents...(Surprise!) How about some input from average consumers like myself who have had more experience with one or both?