I own a Manfrotto Pro 055, a Night Stalker, and my buddy has the Slik. I've used all 3 quite a bit. Of these, IMO, the Manfrotto is the best, Slik is 2nd, Night Stalker is 3rd.
Not knocking the Night Stalker at all, it is a decent entry level tripod and it will be hard to beat the tripod/ballhead price. But the Night Stalker is just not as rigid as the Slik, and not even close in quality to the Manfrotto.
You can get a Slik for $99.00 just about everywhere, add a decent ballhead for $150.00 or maybe even a little less.
As far as hands free, I use the Pig Saddle on the Night Stalker. The above mentioned Reaper Grip is similar, both are clamp style.
But for the best stability look into a direct mount. You will need to add a connection point to your rifle, I have a picatinny rail on my rifle and a Cretac picatinny rail to Arca Swiss adapter that clamps directly onto the ballhead on my Manfrotto. Mlock and Keymod rails are two other options that mount pretty much the same way but I don't have any experience with either of those.
A direct mount will be less expensive that a clamp style mount, and IMO it is better. The biggest disadvantage is that you can only use rifles that are set up to direct mount and with the clamp style you can pretty much use any rifle.