So I have been thinking about building the following rig. My question is quite self explationary. Can I run heavily modded Oblivion?
Also, it would be very appreciated if someone would tell how well these components work together.

- LG GH22NS50 DVD-RW
- Samsung Spinpoint F3 1TB
- BitFenix Shinobi
- Intel Core i5-2500K, 4 x 3.30GHz, 95W, boxed
- Windows 7 Home Premium 64bit SP1 FI OEM
- ASRock Z68 Pro3, Z68
- XFX Core Edition PRO 450W
- Sapphire Radeon HD 6850 1024MB
- Corsair Vengeance DIMM Kit 8GB PC3-12800U CL9-9-9-24 (DDR3-1600)

Gonna buy it on PC this time because of the 5ft anniversary edition.

I expect that it will run modded Oblivion just fine. Depending on what you mean by "heavily," you may get some frame rate drops in places where there are a lot of NPCs, etc. Oblivion tends to bottleneck at the CPU, and doesn't really support multithreading much.

Thank you for anwering.
Could anyone give advice about their compability (sorry if spelled wrong!)
to each other / better components at the same prize?

Also, by heavily I meant maybe some texture or graphic mods.

You should be fine for heavy mods for the most part, but the game engine does still causes drops here and there with many NPCs as mentioned. The Radeon 6850 is no slouch for this 5 year old game though.

The components you chose are pretty good. AsRock did well with their Sandyridge line-up of boards. The XFX PSU is a rebadged Seasonic, which is quite reliable...and the memory and HDD are excellent choices.