Buzzkill is correct that an adjustable voltage mod (such as his own
Buzz) will allow you to set the voltage (and the resultant power, i.e., watts)
exactly to your liking.
However, such a device (or
any higher voltage mod) will be considerably larger than the eGO (and more expensive). Not ungainly: there are so many of us here on ECF who love our large mods. But, if you like the size of the eGO, an LR atomizer may be the way to go. I suggest that you try an LR atty that is
somewhat lower than the standard 510's 2.3 ohms, e.g.,
Ikenvape's or
Indy Vapor Shop's 2.0 ohm 510 attys, rather than plunging down to 1.5 ohms right away.
And, before getting just two more 650 mAh eGOs, check out the 750 mAh Riva and 1200 mAh Hello 016 ... or the new 900 mAh mega eGO batteries.
BTW, you mentioned wanting to use your cartomizers. Since you have the Vapor King, I assume that at least some of those cartomizers are Kr8. CigEasy has just come out with a 750 mAh eGO-like PV for Kr8 cartomizers, called the Elegant. You can read my review of it
here. The voltage is about the same as the eGO, although the mAh is somewhat higher. It also works with the 901 atomizer (no adapter needed) and the 510 (with adapter). Both fit in the Elegant's cone. I'm often using it with the 801 atty (with adapter), although it won't fit in the cone.
And even a true 3.7V PV might meet your needs. Have you ever tried using your 510 atomizer (with a 901-to-510 adapter) on a fully charged Vapor King battery? Such a battery starts out at 4.2V, appreciably more than the eGO's 3.4V. If you like it, you might like a 3.7V mod (many of which are smaller than high- or variable-voltage mods).
You can explore the world of mods with ViZi's
comprehensive guide, the
Custom Mods portion of which describes the eGO and its cousins (but does not yet include the Elegant).