BAT VK-31SE with 6H30-DR NOS tube

Many people here indicated that the BAT VK-51SE is better than the VK-31SE, which should be the case. Whether it is worth the extra $$$, that's a different story.

According to BAT, the VK-51SE are using 8 6H30-DR NOS tubes whil the VK-31SE are using 4 regular 6H30 tubes.

My question is that has anyone compared the 31SE and 51SE with the VK-31SE using the 6H30-DR NOS tubes as well? BAT charge $200 for each of those tube but other tube stores seems selling the 6H30-DR NOS tubes for a lot cheaper.
Apparently Victor has a nice stash of the NOS DR tubes and provides them as stock with the flagship 51SE. Obviously the DR tubes will not make the 31SE sound as good as the 51SE. The 51SE is IMHO substantially better than the 31SE but it is up to the buyer whether that difference is worth the extra cost. Get some of the lower priced DR NOS tubes(you only need 4) and see if they improve your 31SE 'enough'. If not, they will not be wasted and you may end up considering the 51SE.
As a former 30se owner, I would be careful when you evaluate the "upgrade" path through BAT. They have some of the most expensive product upgrades I have found, (Ayre is a great example of how it should be done), and when I compared the 30 and 31 there was no where near the difference that the price of the upgrade would denote. If you are looking for more performance you should really just look at a 51se if you like the BAT sound. I gave up and got an Aesthetix Calypso which I found to be a better overall preamp that you can also tube roll with fairly inexpensively because it uses a more common tube set.