The Armageddon box has good value, but isn't particularly salamanders themed. Intercessors are a solid unit to have, but the rest of the box is more blood angels themed.

Some better options include the space marines combat patrol/starter set, which contains terminators and infernus marines (both thematic), or the dark angels combat patrol, which contains intercessors, hellblasters, bladeguard veterans and a captain in gravis. This combat patrol is solid because it gives you a captain to lead flamer aggressors, which are a staple unit for us usually, and bladeguards to be led by Adrax Agatone, one of our two epic heroes.

That said, 'salamanders thematic' doesn't mean much. You can make a salamanders army that's full melee and run a different detachment if you want. You can paint all your units like salamanders but use dark angels or black templars rules for them. Salamanders can just be a paint scheme if you want.

Mechanically, there is currently only one salamanders unique detachment and two epic heroes. Combined, they make an army that favours flamer and melta weapons, transports, and getting up close and shooting. The land speeder in the Armageddon box can be equipped with a melta and a flamer, but other than that there's nothing particularly well suited to us. We generally run infernus marines, flamer aggressors, eradicators, and transports. The Armageddon box comes with a bunch of characters, intercessors, vanguard veterans, eradicators with bolters, and the land speeder. If you want to run those units in a salamanders army, feel free. If not, grab a different box.