Can anyone recommend batteries for 8S Xmaxx?

Have some cheap HRB batteries but would like at least one extra pair for the xMaxx and maybe for the Maxx as needed. I know people recommend SMC batteries but I have no idea which specific ones for the size, discharge rate, etc. I kinda don't understand them haha.

I could just buy some 6700 4a Traxxas batts but they're pricey.