For tactical shotguns I just don't believe in the high price stuff that companies are trying to sell, OK, if you need 15 round capacity pump 12ga your options are going to be slimmed out a bit, I have held the uts, it feels cheap to me, IMO there is a reason the uts sells used for around 50% of its new cost lol, there is a video on youtube, I haven't seen it in a while but one guy says "so you like it?" the reply is "yah if I had to go to battle I may take it over a pellet gun", I have seen a few used for under $700, there is one on GB rite now for around $700... What I hear is they are junk..
Now for the keltek I own one, bought it used/never shot and played with it a bit, its also kind of junk, nothing I would EVER put in my bedroom for home security...
NOW that all being said, if you want a shotgun, don't get a pump... Get a semi, mossberg 930 comes in 8 shot {I own}
Mossberg 930 8 shot 18.5" #85360 .12Ga NEW! : Semi Auto Shotguns at GunBroker.com {they also have a pistol grip version, I like and own the one in the link} and I promise you go to battle against a well taken care of 930 with one of the above pumpers, you will need a priest... Another semi to consider, and the things I hear are hit or miss with it is the Saiga, some people love it, I own one and haven't shot it a ton, but like...
AK-47 Saiga Izhmash 12ga. Shotgun sbs short AK47 : Semi Auto Shotguns at GunBroker.com ...
I am not sure what the point of high cap 12 gauges are, they used to be the "go to" home defense weapon but people love them and they sell {and I own a few myself, lol} but if you can't get it done in 8 {12ga} then you only need one to turn on yourself, lol.... I am not a fan of shotguns for home defense unless its 410 self defense rounds in a gov. revolver with the ct grips and strobe light... In my bedside lock box I have a scorpion 1911 rail gun with a strobe/laser mounted on it, and Grizzly 175 g xtreme rounds
http://i.ytimg.com/vi/7fvUhGp0mRc/hqdefault.jpg ...
If you just want a bad ass shotgun, I would personally get the 930 spx {no pistol grip} with a bulldozer
Elite Tactical Advantage rail sytem with an undermounted projectile launcher
ST 12 Rear Loading Havoc Launcher [STH1210] - $329.95 : Spikes Tactical you would be under the cost of a 15 rd pump with the 930, rail, and launcher...