I am actually "dwelling" (still) on the shotgun stock question too. I have a good 'ol Remington 870 tactical which I bought new about 4 years ago ($400?). It came from the factory with a hollow full buttstock but I wanted the option to minimize size as much as possible (32"). I did not know much about what after market options were so I stuck an ATI 6 position stock (M4-like) on it until I got around to doing the research on what was available. Four years later now, I have the shotgun just the way I want it---all except for the stock. I actually like the stock quite a lot (even though it is pretty basic and cheap) except for the fact that the gun kicks like an SOB. Honestly, I am not at all afeared of recoil. I grew up with an 870 and I have owned a .375 H&H magnum since my time in Alaska (lived there for 20 years---Seattle now) and I have never complained about recoil on ANY gun until I put the ATI on this 870. I don't know what it is. The first few shots are fine but I do not especially look forward to shooting the fifth.
I am looking at a Blackhawk Spec Ops "KNOXX" stock (about $100 at Brownells). There are a few very well done video's about this stock on YouTube. From what I can see, it looks like it actually works! Phoenix Technologies makes the "Kicklite Sporter" which is a full stock and they have telescoping options as well. I do not know a thing about these stocks but hey are worth a look.
Putting together a perfect .12 gauge is fun. Also, it is worth doing right because they are such a work-horse of anyone's tactical weapon collection. Have fun putting it all together! (photo's of mine attached for ideas)
Remington 870 tactical
ATI six position telescoping stock (converts into just pistol grip too)
H&K sling mounts
XS Ghost Ring iron sights and picatinny rail (factory)
American defense QR site mount
Insight Technology MRDS (3 MOA) w/ protective shroud
Streamlight TLR 1 (w/strobe function)
Total: about $1300-$1400870-1.jpg870-2.jpg