顯卡既分別

唔洗理佢DDR幾 同幾多bit
you can use any PCI-E interface display card, no matter it is DDR幾 同幾多bit, for better performance, you should match with your CPU and power supply(some display card consume higher power, need a higher output power{watt})

同埋 PCIE X16 同PCI X1 係唔係都係可以插顯卡
Both of them can insert a display card, but most people using PCI-E X 16, as PCI X 1 is old design and the transer rate is very slow, just x 1, and the mainstream is x 16, unless your motherboard just have PCI x 1 interface slot.

Finally ,there should be PCI X 1 Interface display card in the market


圖片參考：http://imgcld.yimg.com/8/n/HA00796919/o/701003130165213873427050.jpg

無錯，你只要買張PCI-E x16既顯卡就可用到，至於記憶體之問題，GDDR3當然好過DDR2，GDDR5又好過GDDR3，128bit好過64bit，256bit又好過128bit，384bit當然會好過256bit。
顯示卡是無可能插入PCI X1 之插槽，因為顯示卡是沒有PCI X1 之介面的。