What about aftermrket stuff? Are rings, bases, stocks, barrels available for this, as they would be for the Remington?
You can find any part for a remington.
You will find few choices for the Tikka.
There are some ring choices, but it is limited because the Tikka has a grooved reciever and manages recoil by having a post on one ring fit into a hole at the top of the reciever.
If you look hard enough you will find weaver/picatinny style bases but you will pay $Texas.
AFAIK no one regularly produces an aftermarket stock for the Tikka. I've never wanted one, the factory stock fits me perfectly.
Any good gunsmith can put a barrel on your Tikka, but you won't need it. If you need really good consistent accuracy then get the T3 Varmint or Tactical. The Lite and Hunter sporter weight barrels are very good (my T3 Lite is a 0.5 MOA gun), but the barrel will heat up quickly like any other sporter and groups will open up with repeated rapid fire. T3s are guaranteed to shoot 3-shot 1MOA groups. I've never seen a sporter weight all factory 700 shoot 1MOA with factory ammo.
The Tikka is the better built gun compared to the 700 and 1500.
Pick one up and compare the quality of the machining. Everything fits perfectly. The trigger is adjustable and almost as good as aftermarket 700 triggers.
Does the T3 Lite feel cheap? Sure, almost every plastic gun feels cheap. But once you work the action and pull the trigger it will feel like a million dollars. Compare the T3 Lite's stock to a synthetic 700 or 1500 and you'll see a big quality difference in the material, stiffness, and casting quality. If it feels too hollow then fill it with a little bit of expanding insulation.
The mag is plastic, but works very well. The follwer in the mag is nice. If you want to feed single rounds just drop one into the ejection port and close the bolt. I like having a magazine. If I need to clear the gun I just pop the mag out and extract the chambered round. No messing with a blind mag or popping a floorplate loose and picking up the cartridges.
The T3 Lite is
light weight. With my Leupold 3-9x40mm scope it is only a couple of ounces over 7 lbs, that less than an unscoped 700. It's a joy to carry in the woods.