Beez is your man to fix anything guitar related in the east. Swee Lee Aljunied is there for anything you want in the world. I think Ebenex has a office in Tampines but its by appointment, its a guitar porn HQ so not everyone anytime can go and play play naughty naughty. Seekz can sometimes be found in the east but he's set up shop at Coronation.
Technically every major guitar brick-and-mortar is in the east, as their all mostly east of the Singapore River. And I think that's east definitively. City hall is just under 40mins via Pasir Ris, like 55 from Joo Koon.
East Side yo. Peace. Our food is good too.