not much traffic here.....
have one of the original PH1 Havaks with the McMillan stock in 6.5 PRC w/ 24" bbl and a VX6HD on the 20MOA rail that is pinned and screwed down w/ (5) oversize screws holding it in place. Also have a Browning X Bolt Hells Canyon Long Range in 6.5 Creed for a few comments.
I like the McMillan HAVAK stock; fat pistol grip and flat bottom and has a very stiff fore end with a stud for a bipod and also flush cups on the bottom for a sling. Lots of room around the free floated barrel. the Browning dura touch stock has a very narrow round bottom fore end that flexes a little and only a dollar bill of space around the free floated barrel. The HAVAK has a really nice trigger; easily adjustable for pull weight and over travel to your preference. smooth bolt, (it was a little rough out of the box and smoothed out after a couple hundred rounds) cocking weight is split in half (top and bottom) instead of all the tension on the up stroke like the Browning, making ejection a little more steady when trying to stay on target with a 90 degree bolt throw. Personally like a shorter 70 or 60 or ultimately 54 degree bolt throw (like a Mark V, but the Mk V action is very heavy); just a personal preference and not detracting from the HAVAK design at all. The recoil lug is part of the action, not a screw on type. The balance of the rifle is perfect; all the parts come together as a whole nicely. Its not a mish mash of parts; the design is well executed for its purpose IMO. It is one of the most accurate rifles i own. The mag release and removal is a 2 handed affair and 1 handed going in for me where the x bolt excels with their design, it can be removed and loaded with one hand (blind folded) because the release lever is on the front and attached to the mag so the mag falls into your hand. The xbolt trigger design is also very good. no creep, very little over travel, very crisp although it is way way too heavy. The mcarbo trigger spring helps a little, although it could use an even lighter pull weight IMO.
The HAVAK is probably as close to custom that you can buy over the counter with NO WAITING time for parts procurement and a smith to assemble and test everything. You will have a SAMMI chamber/throat vs a custom which isn't necessarily a down side depending upon the bullets you plan to shoot.
In the end i'm thinking that you couldn't go wrong with any of the choices you are considering. might just give the edge to the HAVAK though.
Oh, one more thing (edit) - the Seekins warranty is for the life of the rifle and not tied to the owner or a receipt for proof of purchase. If something is wrong they will make it right without question. So that would be the best warranty in the gun business IMO.