First time purchasing a barrel. Want an M4 preferably with an A-frame style front sight/gas blockbarrel nut already attached.

There are a lot of choices out there: Chrome moly, chrome plated, Melonite?

In the "good, better, best" category I'm looking for something good to better.  Any suggestions? Best bang for not a lot of money?

You need to make sure your terminology is correct.
- Chrome moly is not a "finish".  It is the core steel alloy from which most barrels are manufactured.
- Chrome (more accurately "hard chrome") is a "finish" but applied to the interior of the barrel and the chamber.  It is very hard and corrosion resistant.  Generally decorative chrome or hard chrome is not applied to the outside surfaces of the barrel.
- Melonite (nitriding) is an all over chemical treatment of the barrel surfaces.  It is black and very hard but is generally regarded as poorly resistant to corrosion.
- Traditionally, steel alloy barrels are "finished" on the outside surfaces with a chemical process called manganese phosphate or "Parkerizing".  It varies from greenish-gray hue to black.  Its not very hard but is corrosion resistant.
- Finally, an alternative material from which barrel are made is stainless steel.  On the exterior surfaces the "finish" can either be natural or black oxide coated.

You sure about the poor corrosion resistance? Fairly sure it's touted as being just as resistant as chrome lining without the inconsistency of being applied in a "coating"

Melonite provides superior corrosion resistance.  Simply google corrosion resistance of ferritic nitrocarburization.  

You are correct.  "Melonite" or salt bath nitriding does offer superior corrosion resistance over plain steel and even hard chrome.  I was referring to traditional carbon nitriding in ammonia vapors that imparts an extremely hard surface but is less resistant to corrosion.

LOL. I had a feeling that you realized that you misspoke. You're usually spot on.

I just ordered an M4 profile barrel from Windham Weaponry (I am in no way associated with the company).  It sounds exactly like what you are looking for.  They're offering 10% and free shipping through the Dec 31st.  

14.5" with a pinned extended A2 flash hider.  4150 Chrome Moly Vanadium 11595E Steel, chrome lined, and 1/7 twist with an A2 FSP.  Comes out to $220 shipped.

https://www.windhamweaponry.com/shopexd.asp?id=284&bc=no

Nice, but a tad much for my budget. What about this offering from CDNN?

http://www.cdnnsports.com/tapco-223-16-ar15-barrel-a2-no-post-spring-detent.html#.VHVWHDHF91Z

seems like a good barrel. if you read though it says and i quote..

"This barrel was produced by a top quality Remington family manufacturer in the USA. Bayonet lug. No front sight post, spring or detent. "

http://www.midwayusa.com/product/155743/ar-stoner-barrel-ar-15-556x45mm-nato-m4-contour-1-in-9-twist-16-chrome-moly-with-a2-front-sight-phosphate?cm_vc=ProductFinding

here you go bubb

Before I bought something like that I would go look at green mountain barrels.  I know first hand green mountain is good quality.  I have questions about that barrel.  It MIGHT be a good one, but I know the green mountain stuff is good.  

 

The product on the Midway page doesn't come with a front sight post, spring, or detent.

I really wish PSA would sell Barrels with A-2 front sight assemblies but they don't. You can buy the sight/gas block and install it yourself or buy a complete upper but there is no in-between.

Great buy.

I have no idea how the quality on these are and I'm not familiar with the brand but I found a couple 16" M4 barrels from DSA that are not very expensive.

1/7 twist chrome lined $145
http://www.dsarms.com/p-11688-dsa-zm4-16-chrome-lined-17-twist-m4-barrel.aspx

1/9 twist not chrome lined $120
http://www.dsarms.com/p-11685-dsa-zm4-16-parkerized-chrome-moly-19-twist-m4-barrel.aspx

I've looked at those as well. Definitely a possibility.

I see that CTD also has the "Tapco" M4 Melonite barrel w/Gas Block A2 front sight for $111 + shipping

This barrel was made by the mfr. for Bushmaster.

Not even with your credit card.

 

My first choice is almost always a good melonite (QPQ) barrel, however, if you don't already have the upper receiver in hand, you might want to give Palmetto State a look for a complete upper, specifically with one of the FN cold hammer forged barrels.

They are high quality, general use barrels...and a great value in a complete upper.



EDIT...be sure to look for the M4A1 barrel profile, its heavier under the handguard, not a skinny little pencil like the standard M4.