There is no performance gain... the Intel CPU you mentioned is a downgrade from your current AMD... Reason why you feel that Intel is much faster in 2D operations + multitasking is due to the fact that you are using an Intel CPU + Intel chipset + correct Intel drivers for XP

The solution for your AMD CPU + ULI (which is ALi before *gasp*) should be new drivers + new bios updates...

Also, don't plan an upgrade if your not getting a Core Microarchitecture CPU paired with an Intel 965 or Nvidia 6xx or ATI Crossfire 3xxx chipset...

For budget PCs, CPU will be a Core Solo CPU or a Core Duo CPU with lower secondary (L2) cache + a 945 chipset..

If you still want an AMD solution, probably an AM2 Motherboard + the cheapest Athlon X2 that you can buy...