all great company's but I have personally dealt with Rob so I know his customer service.. he actually threw in an overdrive pulley for free with my alt so I could get close to 230+ amps at idle and still well over 270 amps at 2k rpm
he can custom make you a larger alternator if you would like but typically the way they are designed the at idle performance suffers which is why when most people run up to 4 alternators they have a master alternator that is around 220 amps peak so they can still have a good at idle voltage
hope you get one that suits you