Tactical Machining is a good company. They are local to me and I've heard good things about them, although I've never bought their parts for any of my AR15 builds.
For barrels, there are plenty of choices. It will really be up to you how long a barrel you want/need depending on your budget and use for the rifle.
I would recommend a Spikes Tactical barrel in 16" from AimSurplus website:
http://www.aimsurplus.com/catalog.as...3&name=Barrels
Although the top of the line ST-FN 16" barrel ($269) is sold out, it is an excellent barrel with a 20,000rd service life!
They do have a 14.5" barrel in stock for $199 that has a midlength gas port, but you would have to permanently attach a muzzle device to it to make it 16" legal length (non-NFA).
There are plenty of other barrel choices from Noveske, Daniel Defense, and FN, etc. Just look online and see which one you want to go with that is within your budget.