the plan was to go with pd1851s but looks like they are a discontinued product I was then thinking the xb1600 but they also are discontinued and from what I can see the 1852 won't fit without modifying the box.

I am not super keen to run tbx100s as when I used to have hogs I had them and upgraded to 1851s. 

The amp I will use to run the hogs is a Pcm20  and I only plan to build two hogs .

Hopefully someone has some good ideas haha

First ferrite model that comes to mind is the RCF LF18X451. PD also has a new lineup with the PD1852/2 and for example the PD.185C003.

PS: 18X1600 is still available as the V2 version. Main difference between the V1 and V2 is the new resistant coating on the back.

i've read a few times about the 18SW115 as a "go to" driver, but these beasts need a serious amp no? as well as the 18NLW9601. 

i have 4 x oberton 18xb1500 in a hog scoop and never was able to really push the sound, all powered on a single 5002vz. 

Now i am thinking about changing my drivers, i want to be sure the drivers can push the sound like expected from a dub/roots sound. 

Taking that into account, are these 18SW115's a good choice? Or am i under-powering them, and should i look out for something like 1850/1852 to have more headroom.

The PD1851 and PD1852 are the same driver, with different recone kits.

I have 4x PD1852s for sale, reconed 2x years ago, but never used.

They are 4 ohm, so somewhat easier to power than the 8 ohm variant, decent amp will drive 2x of these per channel with ease.

The few will know, put 4 ohm driver in Scoop, and the impedance of the cab, will actually be approx 6 ohms.

This has been verified previously, using DSP on Powersoft K20 DSP.

Also, forget about using the trusty old MA5000VZ, to power more modern 8 ohm drivers, at best, it will just about power 2x PD1850s per channel, as they really are just 800W drivers.

Will do bit better, with 2x "4 ohm" drivers per channel.

To "properly" power 2x 1851/52s per channel, you need Void Infinite 8MK2 or similar.

On paper, many amps profess to having higher output power at 4 ohms, like Crown ITECH 8000, Matrix XT7000MF, but in reality, Inf8Mk2 walks all over them, on sub notes down to 40hz.

This was observed/proven in amp sub test, few years ago.

Oberton 18xb1500 can definitely be pushed and go very loud in hogs , I've driven four heavy of a k20 many times never burnt a driver  , their cones fall apart tho after a couple of years . Very light cone for the strength of the motor but that gives them their specific dry sharp sound.

So it's not the driver but not enough power or wrong DSP settings.