Does this combo require the stormrider fill probe to fill with the included pump?
Yes, the stormrider probe comes with it
Is it possible to mount a scope on thIs rifle . If so what will I need besides the scope and rings ?
All you need is the scope and rings, the rifle has an 11mm dovetail rail built into the breech
Which type of .22 cal pellet has the most knock down power? Im wanting the gun for small game hunting.
The JSB 18.13 will probably give you the best accuracy/knock down power out of this rifle, but each gun is different so you'll want to test a few. I'd also look at the H&N baracuda pellets.
is there any significant noise level difference between the .22 and the .177 ? thx.
No, so long as you don't use a pellet that is too light in the .177 which may result in it breaking the sound barrier.
How much does just the rifle (.177) weigh? AND how does the discharge noise compare with other PCPs guns', especially Benjamin PCP?
The rifle on it's own is 5 lbs. The noise level is higher than a Marauder, quieter than a discovery/maximus. You'll want to use heavier pellets so you're not breaking the speed of sound which will result in a much louder noise.
Whats is the best weight of pellet in .177 for this kind of velocity
I have tested this gun in .177 caliber with both light weight (RWS diabolo) and mid-weight Crosman Premiers and JSB Exacts and it only gives a slight hint of supersonic crack in the RWS diabolo which is 7 grains and is relatively quiet with the mid-weight Premiers and JSBs.
In .177 I would recommend the heavier pellets like the 10.3 grain JSB heavy or the H&N Baracuda at 10.65 grains