I bought a "Well Used" 835 from a neighbor for $50 earlier this year, then spent another $150 for an 18.5" Heavy-Walled Security Barrel, and a Heat Shield & shipping at Mossberg.
Later while watching the EE Thread "Shotgun Parts & Accessories", I purchased from one member, an 835, 24" Rifle-Sighted, Ported, Rifled, Slug Barrel for $90 shipped, and from another member an 835, 28" Vent-Ribbed Choked Barrel for $100 shipped.
With all the other parts I've purchased from places like Choate and GG&G, I now have a little over $525 into her.
And now I have a barrel for all seasons, and a my 835 will Feed, Shoot & Eject every 2 3/4", 3", & 3.5" 12Ga. Shell that I can put in the Mag Tube or the Chamber.
And I even got lucky, because my 835 will feed, shoot & eject the Aquila 2.5" Mini-Shells, when I can find them. I don't usually have any issue's finding the Aquila 1 3/4" shells locally, but their 2.5" shells are hard to find.