Your going to run into several problems staying in with tube mods. There's a much larger and cheaper selection in the box types.
First, most of the tube mods on the market are going to have a max amp draw. A 1.6 ohm atty at 3.7 volts (2.3a) is already close to the cutoff for amperage in the provari and lavatube.
The other is the battery's the tubes use, your only going to be able to push one so far before you start losing power.
Im not going to throw a bunch of numbers at you because you probably dont care, and, I haven't done ohms law on paper in a long time and I dont want to be that guy
Basically, your going to have to go unregulated amperage to get any more out of low res dual coils, or your going to have to get a higher resistance dual coil.
I know the IPro and Buzz pro can handle it. There may be other options out there, I cant give you a huge list.
The buzz has a 15 watt cutoff. So if we consider that electronics are always perfect (and they are not) that means the max voltage you should be able to get out of a low res dc is about 4.898 volts on the buzz pro. Its probably lower because of battery's and electronics
Anyone out there feel free to let me know if my numbers or off or I didn't take a certain variable into consideration here.
EDIT: I just wanted to say also that all the advice from the mynameisrob and dormouse is right on. I rock a single coil 3 ohm carto on my buzz pro almost exclusively, and I use LR stuff on my KGo almost every day. Taking a dual coil over 4 volts in my opinion, is not a pleasant vape. I mean, there are people out there that refuse to buy LT's and Provari's strictly because of the amperage limit or step-down measures on them and to each their own but I don't care for burnt juice.