Not much available for the Stormrider to my knowledge. The other guns noted will probably all have a much wider range of "options" whereas the Stormrider is simply a light, accurate, and relatively powerful air rifle at a low price. If the customization potential is valuable to you, I'd probably skip the Stormrider. Depends entirely on what one wants.
One nice thing about the Stormrider, seeing your last post, is that it has a pretty good set of open sights. I've used mine with and without a scope and it works well either way. They aren't particularly loud but probably more noisy than the other guns with "options" could be made.
I have a Hatsan Flash .25. I was amazed at the accuracy and also back yard quiet. 199.00 refurbished. I can get 1 hole groups @ 30 yrs. Having a smaller air cylinder, hand pumping would not be too bad. I actually bought a 2nd Flash for friends to shoot. Also very simple to change o-rings and tune.
Check out the Nova Freedom/Seneca Aspen. It's an all-in-one PCP with a hand pump built-in. It is $400.00 and you can use an outside source for filling if you do get a separate hand pump or air tank. There's always a few issues with some new air rifles and they are sorted out quickly, as you can see in this thread: