My 2 cents. I am not a door kicker either, however I feel if you are going to have a firearm .... it should be the fit for your NEEDS and be the highest quality possible. BTW, there is alot written on here by GunCat, COSMO556, and JD McGuire. I take their words as gospel, they have alot of experience and KNOW WHAT WORKS and what will not.... Identify your needs (you did that HD..SHTF) and meet those needs as best you can within your budget. Also, pattern your scatter gun at various distances so you know what it is doing and shoot it alot (birdshot is great to practice technique.....).YMMV, lather rinse repeat....
1) Dump the Choate tube......(I have one and I was very unhappy with it. I will not even put mine on the EE.)
2) Bead is ok, WORK WITH IT before changing it out.
3) Add some Uncle Mike's Quick Detach sling swivels, some one inch webbing and tri-glides and you have your sling.
4) Not sure what kind of stock you have, if it is pistol grip, dump it. I like the SpeedFeed II, high quality for a little money. There are also Remington synthetic take offs on the EE for $40.
5) There is a light mount that attaches between the mag tube cap and barrel band and had a small of rail. Put a TLR, X3, M300, Surefire G2 in a 1" scope ring, whatever on it. COSMO556 swears by this rig.
I personally tried many different options and I finally broke down and got a Surefire 618 FA off the EE. It adds some weight, but I wish I had not spent a bunch of time and money on "other" options. The only other option I would use would be a QUALITY mag tube extension (Wilson, Remington, VANG COMP) with a laserlyte tri-rail or the Mesa Tactical mag clamp with rail. I have a VANG mag tube and it is great. Had I not got a deal on my Surefire I would have gotten the Mesa and used my Surefire Millennium on my Vang tube. Now the Laserlyte is on my backup while the Surefire is on my primary.....
I am also not a fan of the Tacstar side saddle. Not too bad, I just do not like it. For rounds on the weapon I like the Specter Gear butt stock carrier with SG CQB sling. The local Marines have them on their shotguns at the gate of their compound......Good enough for me....
Here is my 870 Express Magnum w/ Vang tube, Laserlyte tri-rail, Millennium light, Speed Feed II (inexpensive stock) and generic 1" sling........Presented as just one option.