Theoretically or practically, you should accept Krsna as the Supreme Person. Theoretically, there is the revealed scripture. You will understand from the Vedic literature, from the great devotees in the past and in the present. For the present, there is Lord Caitanya. Lord Caitanya is the great authority.
None is greater.
He was mad after Krsna. They have written volumes on Krsna. He is known to have written the Srimad-Bhagavatam and other literature on Krsna. Srimad-Bhagavatam is nothing but a description of Krsna. Vyasa is also the writer of the Bhagavad-gita.