So... Just my $0.02 for those who are interested, but I bought the dual single direct from Burson as an upgrade for my Little Dot 1+, and I can say without a doubt that it was some of the best money I have ever spend on mods for a unit. With the right tubes on the input stage, it basically doubled the sound quality. It is just a bit warm with great bass, but without the highs being sacrificed. I can't speak to using it in any other units, but I am very happy with the application I am using it in.
Now, dealing with Burson and their terrible communication while shipping took weeks to even happen is a totally different story. Not even mentioning that the price I paid was nearly double this drop. I may buy one or two of these to try on other units in the future. YMMV..
KbaumBest match I have found so far are late 50's Sylvania JHS-5654/6AK5W. Maybe not the bassiest, but all around fantastic 6J1 replacements for fairly cheap compared to what I've had to spend on 6DJ8 or 6SN7 NOS upgrades over the years.