Well, oblivion is a demanding game and you need graphics horsepower to run it. One thing that is nice about it too is, it's written for dual core. I have no idea what your budget is so, i'll do my best for you. I'll throw some parts for an Intel machine first, one that I use to play oblivion on and it rocks. Then, i'll give you the specs for my AMD Opteron machine.
In the gaming world and to be honest, it really doesn't matter what processor you use. Yes, you'll get less framerates using Intels in some games but, as long as you have a good graphics platform, it really doesn't matter. If I could show you oblivion on my two primary gamers here, you won't see a difference at all.
Here goes, Intel first:
Motherboard:
http://www.newegg.com/Product/Produc...82E16813131534
Processor:
http://www.newegg.com/Product/Produc...82E16819116238
Graphics:
http://www.newegg.com/Product/Produc...82E16814150139
Newegg is currently out of stock on this graphics card. Zipzoomfly is also. Not sure who has it currently if anybody.
Power supply:
http://www.newegg.com/Product/Produc...82E16817103932
I use this unit in both of my primary machines.
Memory:
http://www.newegg.com/Product/Produc...82E16820146567
I overclock so, I use higher speed memory and happen to like micron ICs. They overclock nicely.
Processor Cooler:
http://www.newegg.com/Product/Produc...82E16835118115
Anyway, you get the picture. This machine plays and does anything I throw at it with ease.
Here's my AMD system that I also game on.
Motherboard:
http://www.newegg.com/Product/Produc...82E16813136166
This board is a great enthusiast board. The overclocking features are endless.
Processor:
http://www.newegg.com/Product/Produc...82E16819103588
The Opteron series use a larger cache and tend to overclock better than their X2 counterparts.
Graphics:
http://www.newegg.com/Product/Produc...82E16814150139
Same power supply as my Intel machine.
Memory:
http://www.newegg.com/Product/Produc...82E16820148009
Again, micron ICs and overclocking headroom.
Processor Cooler:
http://www.newegg.com/Product/Produc...82E16835118223
I have dual monitors on each machine. All of them are Samsung 19 inch 930b. I caught them on sale when Samsung phased them out so I bought em up.
Anyway, either of these two machines will do a nice job for you. The AMD machine is cheaper to build and would fit your budget a little better if that's an issue.