@ SouthernBelle -
Well, you're in luck - the standard Echo-E dual Coil available from MtnVapor.com is a "mid-resistence" coil specially designed to not screw up standard batteries. It is 2.2 - 2.3 ohms, so a little lower than normal, but a little higher than Low Resistance carts...
...and yes, you are totally correct to be careful, the circuitry on most EGO, KGO, IGO, VGO is no rated to drop below 2 ohms, where you get the dreaded "Flickering LED of Imminent Doom" as your circuit board fries itself.
I personally run the 2.2ohms on a standard EGO battery clone (not Joyetech) all day, and have never had the led flicker even once. But, if that level still worries you, the ECHO-E single coil is available from nhaler.com at 3.2ohms...
...and I will say this, because the coil is wider, it still provides a very warm and full vapor at 3.2ohms. In some ways, it is a bit of a mystery to me, because I've tested it and it is definitely 3.2ohms, but it puts our one of the best puffs of all cartos I've ever tried...
Now, the only LR ECHO is the 808 fitting (it won't fit your IGO, so you won't need to worry about accidentally getting one), they built a special LR battery for it, and adjusted the fitting to make sure 510 EGO style users don't accidentally use it and fry their batteries with it. They really are a great company to tend to the small details like this!