1- It depends, for gaming, an athlon fx 57 or an athlon x2 should be better, for video editing, business or multitasking pentium D is fine.
2-Agp is good, so pci express, but the latter is the new standard.
3-To me, In that same order...
Allright, so is the dual core thing not that good cause I wanted to get a 64-bit/dual core and an intel one is like 250 but the AMD ones are like 800.I liked the Fx-57 but i don't know if its out yet or how much it will be but probley alot. I like amd more than intel but intel was cheaper this time so, nmot to sure. I am going for another gamming pc from my current one. Also u said MSI was the best in the order i gave u?
No. If you're going to go for gaming, a budget processor would be the AMD Athlon 64 3500+. If you have the money, wait for the FX-57 or just get the FX-55. Dual-core processors don't really improve overall gaming performance. They're designed to be for intense applications and heavy multitasking.