Quoted:
I transitioned from a LWH to this: Viper

I love it. Exceptional fit and quality. I really love the Team Wendy camfit and the Wilcox mount. From an old ACH, to LWH, this is far superior. Best fitting and balanced helmet I have ever used. I run a single PVS-14 and Peltor COMTACs without a counterbalance and everything stays where it needs to be. I had an unfortunate injury while still active when my NVG shifted my LWH while on the move, but no danger of that here. Even if you don't do this helmet, I suggest the Team Wendy camfit. But after the CamFit (104.95), rails (83.00), and a Wilcox shroud (61.09) you have almost made up the price difference.

It is MIL/LEO restricted so if you aren't that's a game ender, but I would highly suggest the guys at Tac Advantage.

Quoted:
How much do you want/need ballistic?  

Non-ballistic "bump" helmets like the Ops Core Base Jump and Team Wendy LTP are "high cut" for communications equipment, come standard with an integrated NVG mounting shroud/interface, side accessory rails, and a greatly improved suspension system.

They're also far lighter than ballistic solutions (i.e. more comfortable for long periods of time), offer better ventilation, and are significantly cheaper than an equivalent ballistic setup.  

Meanwhile - if I needed ballistic dome protection, I would probably save up to get the best helmet I could afford.  

What're you planning to use it for?

~Augee

PASGTs are the older USGI helmet. They're usually $50-75. They're widely available, but heavier and less comfortable. although they can be upgraded with various pads and chin straps.

ACH/MICH are both the same helmet. MICH refers to a helmet system which includes the ACH as one component. Lighter and has a higher ballistic rating than the PASGT
They're available in 3 styles/cuts:
2000: standard cut helmet used by big army
2001: High-cut helmet with the ears removed for comm systems
2002: Mid-cut. With the ears cut back slightly.
Brand new, all these helmets run ~$500. 2000 cuts are widely available second hand for ~$200.
They're all also made by a host of different companies. Gentex, Revision/MSA, BAE/SDS and some other smaller contractors make these for the DOD. Rabintex also builds a version for the IDF.

LWH: USMC issue replacement for the PASGT. Same cut as the PASGT but uses more modern materials like the ACH to make it lighter and more protective like the ACH. These can be found used but it's much harder than the ACH

ECH: An enhanced version of the ACH with more modern materials that allow it to have better ballistic protection..

Now the really nice stuff:

Ops-Core FAST: Very popular modern choice of a helmet. Typically high-cut with ARC rails and a 3-hole mount pattern. Lighter with a better suspension system than a standard ACH's pad system. These are popular in the SOF (and well-funded SWAT) world. Run $900+ They can also be had in high and mid cut as well as a "maritime" verison ($1100+)

Crye Airframe: Lightweight, uses a pad system instead of a suspension system. Comes with ARC rails. The biggest innovation they bring are that they're a 2-piece helmet to allow air to flow to the top of the helmet. Run $850+

Team Wendy Exfil: The newest "cool-guy" helmet. High-cut and apparently very light with Team Wendy rails. Runs $950

There are also some "off brand" helmets. Some companies have built helmets using the ACH material to make PASGT and ACH style helmets. Many of these retain the PASGT hardware locations and come with either a modernized suspension system or pads. Pro-Tec was making these types of helmets for a while. There's quite a few to list them all. A popular brand of these are Kejo, because their High-Cuts sell for ~$300.

There are also knock-off versions of the FAST. Basically other companies use the FAST cut (slightly different than a 2001 ACH) and use more available materials and pads, and add ARC rails, OpsCore shrouds, and the same cuts of velcro to make them look like Ops Cores without having the lighter materials and suspension system. These are much closer in price to the ACH helmets than the Ops-Core. However, the companies doing this are usually foreign and much less reputable than the above brands.

Quoted:
I'm not an operator so ballistic protection is completely optional. I'm trying to say as much under $400 as possible so it looks like my only options are non-ballistic. Ops-Core helmets are awesome (used one at my last base) but expensive as hell. The Arma-core clones are a bit cheaper and so far the EE listings have been closest to my budget. I currently have an ACH-cut helmet and it sucks not being able to wear my MSA Sordins or Howard Leight Impact Sport earpros under them.

Quoted:

BTW whats the rails on that helmet in your link?

i didnt think Ops Core made rails that fit the High Cut ACH. Their normal ACH rail only fits the regular and medium cut.

Just for reference i use a MSA rail on my high cut ACH

Quoted:
Arma Core makes a ballistic helmet cut exactly like the FAST. I don't know anything about them (and I've checked all over the interwebz, got nothing other than their website), but they are made in the US and include all of their ballistic testing data on their website, if that makes any difference.

Quoted:
https://farm9.staticflickr.com/8645/16085831348_634b2e345d_z.jpg

Also worth noting that the ACH ARC rail does not fit ACH 2001 high cut helmets. I found this out the hard way and out of desperation went with a air soft scpy of the MSA style ACH rail.

As Augee the helmet is probably not a true ACH 2001 cut, but even if that is the case im not sure whats up with these rails.