Why didn't Shlomo use Kodshei David to build the Beis ha'Mikdash?
Rashi: He did; this was the gold and silver that remained from David's Hekdesh.
Rashi and Radak, both citing a Midrash: Shlomo did not want to use what David was Makdish for the Beis ha'Mikdash. I heard that Shlomo knew that the Bayis will be destroyed. He did not want the nations to say that their god took vengeance, for it was built from what David stole from them. 1
Rashi citing a Midrash: Shlomo said, there was a famine for three straight years in David's life. He should have used his Hekdesh to keep the Aniyim alive! 2 Radak - therefore, the money will be kept for a time of need (if there will be a future in the future, to 'fix' David's mistake - PF).
Radak: Amidst Shlomo's great wealth, he did not need David's Hekdesh. Even so, for his father's honor he used part to build the Beis ha'Mikdash, and put the rest in the storehouse of Beis Hashem.
Malbim: He did not need it.
Pesikta Rabsi 6 and Yalkut Shimoni 186 say that David was concerned for this, and prayed that Shlomo should not need David's Hekdesh. (PF)
Pesikta Rabsi 6 and Yalkut Shimoni 186 say that Hashem was upset with David for this, so He caused that Shlomo would not need David's Hekdesh. (PF) 'Rashi' (Divrei ha'Yamim II, 5:1) - the Midrash says that Shlomo put in the storehouse the gold and silver that David was Makdish, but not the great amount of copper that he took from Hadad'ezer (Divrei ha'Yamim I, 18:8). Shlomo made the Yam from that. According to the simple meaning, copper is cheap, and it is not proper to bring it into the storehouses of Beis Hashem.
Which Kelim are these?
Radak: It is what David took from Hadad'ezer and other Nochrim (Shmuel II, 8:7-12).