I have no doubt that trying out that sniper coil will find you a little more.
Most that mount this thing are shocked at the things they find at sites they have hunted over and over with larger coils including their own front and backyards.
Masking is a bigger problem than most believe, and just the precise nature of this type of coil will give you a few more targets to dig, I am sure.
I have a big DD on another detector so I don't think I would need to spend the money on that DD coil for this one.
I did invest in a 10" coil for those times when I need a little extra depth over the 8", although I rarely use it because that sniper is mounted most of the time.
Half the price of that DD, deeper than the 8" and a good choice, value wise, if you want to see what might be a little deeper after cleaning that site up a little more with the sniper.
My 8" is all but retired now, I can't see any reason to use it when I have the 10" and that sniper.