Computer advice

[MarshalLaw]

Hello all,

After 4 good years with my old computer I'm finally upgrading. Of coarse I want something that will play SH3 and the upcoming SH4. I have read some of the post regarding vid cards and such. However I have 2 questions:

DDR vs DDR2 Ram.... Is it worth the extra cost?

ATI Radeon vid cards vs NVIDA which is better graphics wise?

Below is what I'm thinking of getting please feel free to chime in your thoughts, I want to make sure I make a "informed" decision.

Thanks,

Athlon 64 3800+939 with a Asus compatible MB
Maxtor HD 160 GB
Best 19 inch Flat screen I can afford
1 Gig of DDR or DDR2, 2 gig if I have enough cash
ATI Radeon X1600Pro 512MB
XP Pro (Upgrade from Home that I have now)
Good case 400watt PS, standard Mouse/keyboard
Floppy/ 16X Rw/=RW light scribe
DVD/Rom
Altec speakers ( nothing fancy)
Sound Blaster Audigy SE

Hoping to keep it around $1000.00 US