There are four Sampradayas from the beginning of the creation. One is called Brahma Sampradaya, and is coming down by disciplic succession from Brahma; another Sampradaya is coming down from Laksmi, called Sri Sampradaya; another is coming down from the Kumaras, they are known as Nimbarka Sampradaya; another Sampradaya is coming from Lord Siva, Rudra Sampradaya or Visnu Swami. These are four bona fide Sampradayas that are accepted by the bona fide spiritualists.
The Impersonalist Sampradaya is not original, neither the Impersonalist Sampradaya or party can help us. Anyway, all the four Sampradayas above mentioned, they are after worshipping the Supreme Lord Visnu, in His different Expansions, and some of them are in favor of worshipping Radha Krishna.
(Srila Prabhupada Letter to Upendra, 02-13-68, Boston)