Those sliders must almost certainly of acted using a logarithmic scale. Are you requesting a linear scale wheel/slider?
DaveC said:
Sliders have to be log because a slider just doesn't have the range.
The human ear works in a logarithmic fashion. That is why most applications (software and hardware) use a logarithmic scale of volume. If using a linear wheel/slider, the volume increase won't sound 'even'. Little difference in volume will be heard in the first half of the scale, and then it will shoot up at the end.
I've voted to have the DC socket at the back, because I think it would be messy and obstructive at the front. I also voted for a volume wheel rather than a slider, because as DaveC said, dust and other grit becomes a problem with sliders, and I've had a couple of items in the past which have become near unusable because of this.
I also don't believe a slider suffers any less from accidental pocket-movement than a wheel. In fact, I'm almost certain it would be the other way round, as a small knock could send a 'slider' from one end of the scale to the other, where a wheel would only turn 1/4 of the way round at most, which could be as low as a 10% volume change, depending on how sensitive it is made.