My "old" addition is a beautiful 1941 Play Ball Ted Williams card that is graded a BVG 4. The card is beautiful, decent condition (especially for 1941) and was won in an auction format which is my preferred method of purchase on eBay.
The "new" addition is a 2012 Topps Allen & Ginter Bryce Harper rookie card. I wrote about this card and the BGS 9.5 population that is likely to surpass past year Allen & Ginter cards. It has the subgrades I was looking for and was at a price that I thought was reasonable. While there is no guarantee that he'll end up in the Hall of Fame someday, it's the "must own" card from 2012 Allen & Ginter.