You can use your 510 attys and carts on an eGo. The eGo battery lasts for @6.5 hours. It is wider in diameter but has the same fitting for the 510 - for appearance and some functionality - there is a cone that fits over the 510 atty. If you get a regular eGo kit you'll get 2 650mAh batteries, 2 510 attys, a pack of 510 carts, a usb charge and some include a wall adapter for the usb charger, and perhaps a cloth case.
But if you're considering the eGo, since you already have the 510 attys, you might consider getting a eGo-t kit. And with the better reports and more ejuice capacity, the B type/cylinder kit might be a good buy.
https://www.cignot.com/product_p/kit-ebt-all.htm
You'll get all the above, minus the cone and the B type attys and tanks in place of the 510 atty and carts.
You might want to pick up a cone in case you want to use your 510 attys/carts. The B type tanks hold 2.5ml of ejuice which can last you about 4 hours fairly heavy vaping and longer depending on your use. The batteries also have an on/off function that doesn't exist in the regular eGo kits.
You can also get the A type in the eGo-t - 1.5ml capacity.
If for some reason you don't like the tanks but would like more capacity than the 510 cartridges, you can get the mega eGo attys and carts - again the B types hold about 2.5ml and the A type 'cone atty/carts' which are tapered - much like the original cone - holds 1.5ml of ejuice.
There is also mega eGo cartomizers, LR attys for the A and B types of the megas and also LR A type for the eGo-ts (and likely LR for the B types to come shortly).
AND ...

you could get 510 cartomizers or a 510 to 901 adapter and get KR8 and Bloog Maxxfusion cartos. So it is one of the most flexible systems out.
eGos are compatible with Tornados from totally wicked and Rivas from various vendors. You can also get even longer lasting batteries in 900mAh (9 hours), 1000mAh (10 hours) and 1100 (11 hours). And a Passthrough that has a usb charger for at home or for on the road with the appropriate adapters.