your components and what do you like to shoot ? Gun and shot ?
I just picked up a Encore 209X12 .
I have the Knight TK2000. I shop the web for most everything but shot. primers and powder. The extra shipping on these items makes the cost prohibitive IMO. If you are near Columbus there are several locations you can get mzl products. I'm sure you will get plenty of replies but Ballastic Products is one name that seems to always come up. I've ordered from them + Dixie Gun Works + Natchez Shooting Supply + Gander Mt + some place I've probably forgotten.
T/C does sell 12ga components on their website minus shot!
Get a lot of my stuff from Track of The Wolf.
Ballistic products inc. has copper and nickle plated shot-ITX turkey trauma 13 shot, every size shot cup you would need, over shot cards. http://www.ballisticproducts.com/
bpi tps(Tungsten Propulsion System (TPS)) or their multi metal shot cups much more economical-get 100 for $12.99-- knight-$11.99 for 20 or tc shotcups $12.99 for 20.
you can also get 2 3/4", 3", or 3 1/2" cups- preslit or unslit--just cut with knife or scissors and test 2 or 3 slits-it does make a slight difference in my gun.
Also Eastern maine shooting supplies has trad. wads, etc, track of the wolf has wads and wad punches
as for powder I use Black MZ by Alliant powders. I have allergies and all of the others bother me a lot. close to same velocity and works very well in my older pedersoli with #11 caps for dove and rabbits. Got 7 doves last year in the one day I hunted.
I made the terrible(stupid) mistake of loading the double with Black mz and did not shoot it off at the end day. I intended to hunt again but a couple of days later I was rear ended and injured my shoulder. completely forgot about the pedersoli being loaded. After several months of therapy and cortizone treatments( make that SEVEN months!!!)
I finally realized (remembered) my mistake. So I took it with me to the range with my rifles and tk 2000. cleaned the nipples with a pick, put a couple of caps on and shot each barrel. both barrels went off and felt just as strong as they did in September!!!!