A seven cell pack is really not needed if you buy the correct brushless setup for your needs, for what it's worth.
You mentioned that you're mostly bashing now.. so I'll assume that you'll be wanting to use the reverse on the esc. With that being the case, you may want to avoid the LRP Sphere - if you hit the brake and hold it for more than a tick the esc jams the motor into full reverse almost instantly. It's fine with reverse disabled, but the reverse is absolutely awful as-is.. it can't be adjusted at ALL on the esc, it's either on or off with the Sphere. The reverse is *great* on the Novak esc's, no issues there. Both brands have had some issues with reliability, we own both and haven't had problems with either. Once you settle on a brand, it'll just depend on how fast you want to go.. are you into big airport runway type speed runs or are you running them in general? If you want to use it in everything you've listed just go for a middle of the road BL motor, should be plenty fast in everything.
Well if it seems to be real, it's illusion
For every moment of truth, there's confusion in life...