I was foolish enough to miss out perhaps the most important chola king who was a very staunch vaishnavite - in this topic.
He comes somewhere inbetween sangam cholas and kochenganan(3AD - 8AD approx) - a period in which we do not have good records about cholas.
He was king dharmavarma chola.
He was relaxing in the kaveri sand bed when he heard a flock of parrots - sitting in a tree and reciting the following sloka : KAVERI VIRAJA SEYAM VAIKUNTA2M RANGA3MANDHI3RAM / SA VASUDE3VO RANGE3SAHA: PRATHYAKSHAM PARAMAM PADA3M // VIMANAM PRANAVAKARAM: VEDA3SHRUNGA3M MAHAD3PUDA4M / SRI RANGASAYEE BA4GHA3HAVAN: PRANAVARTHA2 PRAKASAKA://
Meaning: River Kaveri is the same as the river Viraja in Vaikunta; The Srirangam temple is Vaikunta itself; The Lord of Arangam is none but Vasudeva; God's eternal abode is here perceptibly; The Vimana is the form of Pranava(OM); Its four towers are marvelously like the four Vedas; And Sri Rangasayee is expounding the import of the Pranava;
The king had enough sense to realize that this cannot be a co-incidence and there should be something to it.
He excavated the area beheath the tree and found the main pranavakara vimanam of srirangam which exits even today. The whole temple got into the sand after dretha yuga when vibeeshana had installed lord ranganatha in srirangam. He is also known as Kili chozhan since he understood the words of sukha (or parrot). (There is an ancient Kili Mandapam in srirangam temple even today.)
He built a modest temple around the vimana. It is interesting that Srirangam deity is called Ishvaku Kuladhanam (The gift of Ishvaku kulam) and dharmavarma came in the ishvaku vamsam or sooriya vamsam.
Later on, king's daughter sengamala valli also became mad after sriranganathar (even a muslim girl loved sriranganathar at a much later date - her name is Thulukka nachiyar!!) and married him at last - just like andal.
Dharmavarma built a temple for her and his mappillai and that exists even today : Uraiyur perumal temple (Thiruk kozhi vinnagaram).
Every year, on a specific day, ranganathar leaves srirangam in secrecy to visit sengamalavalli. Not tolerating this behaviour, ranganatha's wife ranganayaki thayar lives in a separate compound in the srirangam temple. She also sits near perumal only one day in the whole year (during panguni uthiram) - that too after lot of cajoling by Nammazhvar!!