Ok, I've got a Rem870 Express, magnum receiver, with a side saddle, and +2 mag extender/sling mount from Wilson.  I want to get a sling (and the buttstock dosen't have a stud), a 6 shell carrier for the buttstock, and mount a light to it.  

I'm thinking Specter SOP is my sling, and they make a shell carrier as well.

For the light, I don't want to do the Surefire forend, it costs more than I have in the gun now.  I'd like to get a rail mount for the mag tube like this and either mount a M3 or a 1"ring and a surefire G2.  Both of those options would beg the question of getting a pressure pad and phone cord attachment for the lights as well.  

I'd also like to get better sights, ghost rings, with a tritium front.  Options there?

Thanks for the input guys!

As far as ghost rings go, I really like my Wilson Combat/Trijicon sights.  They are available with only the front illuminated or both the front and rear illuminated (3 dot style).  I have the latter.  

Ghost rings, whatever the type, are really a great improvement over front bead only.