I don't know about Pheonix, but in Tucson, Peter Hills (
[email protected])is one great guy to deal with.
You can also look atthe Bowers Recommended dealer list...
http://www.subguns.com/c2c3/c2c3.htm
The MG and the silencer (supressor) are separate items so each require a separate stamp and thus $400 in tax.
With a registered receiver M16 you can go safe-semi-full, safe-semi-3rd, safe-semi-3rd-full. It just depends on which fire control parts you put in the gun.
Personally, I wouldn't deal with Advanced Armament. They're a little cheaper, but their supressor designs look like they were stolen from GemTech IMHO. GemTechs are the top of the line stuff, fairly affordable, and they pay attention to customer service even long after they've made the sale. You have a problem with a Gemtech, and you can be sure they'll take care of it.
A registered receiver M16 will run you anywhere from $4500 to $10,000 depending on the model, manufacturer, condition, etc. Godd quality conversion guns are available for about $5k, but you're not going to score a factory Colt M16 for that.
How much are you looking to spend?