Procharger,
As fellow THR members have pointed out, there are several 16" Bushmasters available without a comp (you can't say that about Armalites). It is commonly known as the Bushy Shorty and there is a Dissipator model as well. I have the Shorty. It is a great carbine and I highly recommend this barrel length.
The 16" really does not need a comp unless you need really quick follow up shots, but you could have a smith put one on if you want, but it would have to be welded or pinned making it semi-permanent. I would steer clear of the 14.5" barrel with a comp - too friggin loud. And besides the total length is the legal 16" anyway - so what is the point other than they are cool looking, especially the AK brake.
Go with the 20" barrel if you want to be a purest. I like the 16" barrel because it shaves almost a pound from the HBAR barrel and makes the AR a very handy and well balanced carbine.