I like the lnger gas system and rail on the KAC.  But my colt is more accurate than the KAC.  What i still like about the colt is that i can replace any part if i want to.  KAC is proprietary and i have no idea how to get that rail or barrel off.

Im all for a knights but with it having non standered parts id probley stick with something that is nato common just for logistics.  People can ask all day long who makes the very best and we all know asshole and opinions.   For SHTF its going to hard to beat the colt. When money is really no object by two or three see what you like best. If money is to be spent wisely and it were me id be more concerend with optic choice. All the rifles mentioned are great including several others but optics have a much larger spread on quality.  Never shot one but I bet that Larue would be a winner paired up with a Aimpoint or maybe a nice high end 1-4.

If a Knight's allows you to achieve levels of snoopin'-n-poopin' otherwise unachievable with a Colt or DD then I'm happy for ya, hard-charger.

RECEIVER MANUFACTURERS
The following is a listing of who machines the raw receiver forgings for whom.
Aero Precision

   Aero Precision

Continental Machine Tool

   Stag
   Rock River Arms
   High Standard
   Noveske
   Century (New)
   Global Tactical
   CLE
   S&W
   MGI
   Wilson Tactical
   Grenadier Precision
   Colt

JVP

   Double Star
   LRB
   Charles Daly

LAR Manufacturing

   LAR
   Bushmaster
   Ameetec
   DPMS
   CMMG
   Double Star
   Fulton Armory
   Spike's Tactical

American Spirit

   American Spirit

Lewis Machine & Tool

   LMT
   Lauer
   DS Arms
   PWA
   Eagle
   Armalite
   Knights Armament
   Barrett

Mega Machine Shop

   Mega
   GSE
   Dalphon
   POF
   Alexander Arms

Olympic

   Olympic
   SGW
   Tromix
   Palmetto
   Dalphon
   Frankford
   Century (Old)

Sun Devil

   Sun Devil forged billet receivers

Superior

   Superior Arms
   Lauer (New)

That list is wong in a few spots (and old), for instance Aero manufacturers lowers for Armalite and Spikes.  ...You shouldn't repost stuff you don't now where it can from and think it is the gospel.

LMT and Knight do have a working relationship going, that's why the LMT MWS uses the same lower as Knight SR25 and they both use the SOPMOD.

Companies change suppliers all the time. That wasn't the point.

There are only a couple foundries and forges in the US that make the raw materials.

The rest is attention to detail and quality control in machining and assembly.

So, my point to OP was that if he already has a satisfactory Colt, no, the extra money won't get him a rifle that is measurably any better (unless his goal is to impress people on the internet).

My thought is that ammo and training (and a spare BCG/LPK) would be the best way to spend the difference.

If you like how the KAC is set-up it's a good value.  With what you would spend to accessorize a 6920 or DD the same would end up being more and  you still wouldn't have all the features of the KAC.  It's a steep up front cost but a good value.

If you are stuck on KAC and Colt, sure.

If you are willing to "downgrade" to LMT, a DD RIS, and others, it will be a tad bit cheaper.

This, I bought a couple Knights lowers, and was so impressed by their quality, I bought a SR15, than after shooting a EMC, I ended up ordering one of those, all the plus's have been stated above, and the ONLY negative is the price, but honestly when you add it all up, and than start improving your present Colt, DD, BCM or Noveske, it all evens up in the wash, and you still dont have a few of the Knights plus's.  My only complaint about Knights is, they wont make a 16" semi version of their excellent PDW

True thanks to the EPA, we only have a few foundries left, but you also forgot that even though we have a limited number, those foundries will also use materials spec'd by the buyer, so even though foundry A makes raw forgings for their buyers, their still not equal, you can find different lowers made from different spec'd aluminum, sure the major reputable manufacturers use the same, but look at the lower teir manufacturers.  The way you say it, your make it sound like BCM lowers are no different than say Oly.

I've had my SR15 for about a year now. I'm still impressed by it. Very light, reliable (caveat below), and always goes bang with at least half decent ammo.

The one problem I just had a week ago; the button for my front sight fell off. I have no idea how it happened. I was running drills, loaded a mag, pulled the rifle up to shoot and the front sight was stuck up. That being said, I've already talked to June and she mailed me a replacement as soon as she got the email. I've had a Troy on top of it for a while now, so the extra weight may have caused it, but I would think they thought that through while designing the rifle.

Either way I'm still very happy with my rifle and happy with the only customer service I've needed so far.

I didn't mean to imply that a Plum Crazy/Oly/Hesse are functionally equivalent to an SR15.

I am saying Colt/DD are.

I know, I was just adding clarification. That even raw forgings are not the same, even though they may come from the same forge.  The devil is in the details.
ETA, I'm not even addressing the cast or plastic lowers, Oly was just a low budget example.

getting back to the OP

yes kac is worth the price difference , at least to me. YMMV

IMHO, no. If you already have a half dozen other quality AR's and just want something different. Then I guess...

That said, even with a half dozen quality AR's....  I would still buy two 6920's for the same price as a SR15 all day long. When a 6920 was $1300-$1500 I think it would be more of a thought, but with 6920's at a grand I would spend 3k (figure $500 each for rails, stocks and BUIS) and have two rifles that I would trust and shoot the snot out of... YMMV

There's also the fact that KAC has an E3 bolt, pencil barrel, two stage trigger, light recoil buffer and about the best rear iron sight. You also get a vertical grip and rail covers. On top of that you also get the build quality of KAC (not the build quality of yourself in your garage) and great customer service that will warranty and service the ENTIRE rifle.

I'm not trying to talk down Colt by any means. But with what you get, the KAC SR-15 is an amazing deal.