hamltnblue - Good set of pictures. I'm not sure of the exact specs of the onboard storage of the HC-2, but I do know that it is twice the size of the HC-1. I have nearly all the current available sounds and lighting effects on my HC-1, and finally ran out of space to add the newest prime mover file, the Alco 539T. That may put it in perspective some. So yes, there is a limit to how much you can store on the controller, but with the HC-2 you will easily be able hold everything that you need. That being said, as the sound library continues to grow it will probably get to the point that even the HC-2 can't hold all the files at once. That's a good thing IMO, as it means that there will be many more available sounds when it gets to that point.
Transferring files to the locomotive modules is time consuming, at least with the prime movers. Loading smaller files like lighting, pictures, and smaller sounds goes quickly for me. Usually a few seconds. The prime mover transfer takes closer to 10 minutes though. I will usually start the transfer, set the controller down and then work on another project while it transfers.
Regarding the sound levels, components of individual sounds cannot be adjusted at this point (i.e. you can't adjust the turbo whine of a prime mover, or adjust the pitch of a bell), but sound levels can be adjusted for individual sounds (i.e. you can change the volume of the bell, the horn, couplers, etc as each of these are their own distinct sound files). Individual sound file levels can be set and adjusted in the Button Setup menu. You can set each button to whatever you want it to be. I have changed buttons around on my locos so that it is easier for me to reach want while using one hand and not looking at the throttle.
I'm a huge fan of the real time locomotive information. It's great to see exactly how much current the locomotives are drawing. You can watch it go up and down depending on the grade of the track....going downhill, the locos will draw less power while maintaining the same speed, going uphill they will draw more. The track voltage came in handy when I used to run at a club. It helped us diagnose where additional feeders were needed, or where the trackwork needed some attention.
-Kevin