I owned the Model 6's for three years, and when threads appear regarding Rowland amplification, I write exactly what John wrote in his first paragraph - everything he wrote comports with my experience. I have a few additional comments.
Regarding power cords, it is important to point out that manufacturers of hi-end two channel equipment, and in particular, amp manufacturers, spend time trying various power cords during the design phase of a product's development and the cord selection is quite important to the sound they ultimately achieve - for example, VAC went through several dozen power cords before settling on the one used with their Renaissance amps. It is therefore not the case that an aftermarket cord will necessarily be better. I never tried cords on my Model 6's other than the Rowland power cords because I ran the batteries and I am not suggesting that you cannot do better, but the process of selecting an aftermarket cord can involve a lot of sweat because they will alter the sound, and not necessarily for the better, on a highly resolving two-channel system. If you run the batteries, the choice of power cord will be irrelevant.
As for the batteries, I spent a lot of time comparing the amps with and without, and ultimately determined that the batteries are essential. Even in a highly revealing system, they will not make much of a difference at low to moderate listening levels. However, at high volume, they make a big difference because the amp remains a lot cleaner due to the absence of noise off the line being amplified. Objectively, they reduce ultimate wattage compared to having the A/C supply engaged, but the amps ultimately have greater headroom for the reason just provided, and this is crucial for persons who listen to music that really challenges equipment (big symphonic).
Finally, all Rowland gear from the mid-to-late 90's is differential balanced, and in a revealing system, will sound best when run in a fully balanced system.
The Model 6's are superb solid-state amps - the build quality was fantastic, and in my opinion, their sound quality is surpassed only by the very best solid-state of today (darTZeel, FM).
Hope this helps.
