WooWee Momma, that do have a bite! (that's a pricy combo)
Have you thought about using Lithium modules out of electric cars?
For example, an 18S3P 72V 50AH battery module, out of a Chevy Volt, (~$750.00)
...would/could easily put-out 200A
...& should power a kart for at least an hour
They are professionally designed & built (to power full size cars NOT RC cars)

...& not some Chinese, who knows what/junk
My Hell-raiser kart has (2) 24V 50AH Chevy Volt modules, connected in series to make a 48V 50AH battery pack
...& I've ran it several times, for nearly an hour each time
Oh...& it's super fun too