Need help on custom built computer parts

[CrzyIcE]

Hi, I am planning to have my computer custom built and I want to know if these parts are good enough:
LG 22x DVD Burner w/ Lightscribe
Sigma Unicorn 1.0mm SECC Steel ATX Mid Tower
(w/ 2 80mm fan, 2 120mm fan, no air duct)
Sapphire Radeon ATI HD 4850 512MB GDDR3 256 bit
Corsair 1000W Power Supply
OCZ 3 x 2gb DDR3 1600 (w/ heat spreader)
Windows Vista 64 bit Premium
ASUS P6T Deluxe LGA 1366 Intel X58 Motherboard
Intel Core i7 2.66 Ghz

1)I also want to have it overclock in GPU, RAM, and vid card so would I need anything else such as a heatsink or more fans to prevent overheating?

2)Is the case good enough? I am not sure how to pick out a case.
Also would the power supply be sufficient enough for a crossfire or SLI?
I listed that I am only getting Radeon HD 4850 but I might upgrade it in the future.
Would a 850 Watt be able to handle these situations? what about a 1000W? or would I need more or is it more than enough?
scenario 1) Crossfire Sapphire ATI Radeon HD 4850x2 + overclocking
scenario 2) Crossfire Sapphire ATI Radeon HD 4870x2 + overclocking
scenario 3) SLI GeForce 260 GTX + overclocking
scenario 4) SLI GeForce 280 GTX + overclocking
scenario 5) Crossfire Sapphire ATI Radeon HD 4850 + overclocking
scenario 6) Crossfire Sapphire ATI Radeon HD 4870 + overclocking
Thanks for your help!

 

[wizzardxexe]

lol that power supply will run your house. 850w would be more than enough
you would probably get the most performance out of the SLI 280 GTX +overclocking, all though the 4870x2 isnt bad either

 

[Whirlwind]

I don't know about the case....but if money is not an issue...those parts are very good indeed.