You can find used furniture on Xiamen Jie (廈門街), a street that is under Jung-Jun bridge, that links Yong-Ho with Taipei City, located at the Ho-Ping West Road and Tsong Ching-South road intersection area. You can also find kitchen equipment, both used and new.
Alternatively, check out the below online second-hand furniture stores:
傢俱賣場 (A list of furniture stores)