New PC, Please help me spec

hi, i need to get a new pc so could you please help m,e spec one up. i use my PC for watching films, surfing net, encoding, video editing, CAD and 3D modelling programs, creative suite and gaming. so my use is widely varied, but my main use is for doing CAD and rendering so if you could please recommend parts based on good performance for my use. i have done a bit of research and have chosen the following components. please suggest any recommendations. i am open to all suggestions as i will not be as experienced as you lot.

amd X2 4400

not sure on a motherboard. i was thinknig of getting an SLi compatible mobo so that in the future i could get a little boost in the graphics area. i would want the best motherboard though and willing to pay up to $300, maybe more if i could be persuaded. i will be overclocking, and i heard that the DFI NF4 boards are good.

BFG GeForce 7800GTX (one at the moment, might get 1 in the future though)

keeping my 2gb Kingston hyperx PC3200 from my old system.

not sure on hard drives yet, but have posted in that section.was thinking of getting twin raptors and then 2 other big hard drives.not sure but if you could suggest which hard drives and hat RAID setup please.

thinking of getting a sound card but not sure whether i will.what are the benefits? if i get oe it would not be an expensive one.about $100 would be my budget on this component.

PSU - im not sure on this one.ive heard a lot about the PCP&C 510 and the OCZ 520.which would you recommend? i dont mind spending good money on a power supply. budget of about $250-300 on this part.

please recommend some moderately priced DVD burners. is the NEC 4550 good?

already got a dell 2001FP monitor.

thanks for your help and i hope i can get somewhere soon as i want to buy the system very soon.

For ocing the motherboard you have now is good, the DFI nf4 Ultra or whatever. The proc is good. Gpu good. For HDDs I dont really know much about the raptors so someone else can tell you about them, but i suggest a Maxtor DiamondMax with 16MB cache. I think they have a 300, probably bigger. For the PSU I know both are good, I suggest the PCP&C, just because i have heard good things. Also I have heard many a time that the NEC 3540A is a good burner.

All seems well, If you do have the budget for the PC P&C Go for it.
DFI For mobo.
You've got the ram.
Video Card is hands down the best right now, and I stress right now. Who knows what will happen with ATi in the next week or so.
Hard drives - - Really don't have a clue. Raptors are always a forum favorite. I think Hitachi drives are excellent as well.
Any overclocking you might want to look into some aftermarket coolers. I've had good luck with my XP-90c so far.

you already got a damn good setup. for the psu, i'd get the pcp&c, those are prety much the best psu's money can buy. most burners are about the same, but plextor's drives are the standard to which all other drives are compared to. since you use your pc for work, i'd ruggest a raid1 array. 2x74gb raptors and 2 large storage drives all in raid1 should work well for you.

lite-on are always good products . for burners

is 150gb (approx) enough space for you ??

Well your kinda aiming to spending a lot of money in the expensive areas.

I'd say get this:

AMD Athlon 64 X2 4400+ $526.00
DFI LANPARTY UT nF4 SLI-DR $174.95
Western Digital Raptor WD740GD 74GB $170.00
Western Digital Raptor WD740GD 74GB $170.00
Maxtor DiamondMax 10 6L300S0 300GB w/16MB $107.00
eVGA EGS Geforce 7800 GTX $474.99
Creative X-Fi XtremeMusic $106.36
PCP&C 510 $200

I'd say get the BenQ DW1640, it has really great reviews and ratings.

Now to answer some of the questions.

A sound card can do the same thing in what a video card does to graphics, it makes it better. Especially the new X-Fis, if you listen to music or play games, most say it actually has a noticeable difference from onboard sound, maybe even from the Audigy 2 series.

I'd say get two raptors in RAID0, since it looks like your budget is pretty high. And get that DiamondMax 10 as backup or for storage and stuff. But if what your doing is pretty data-sensitive, and all your files are important, then maybe getting RAID0 isn't too great of an idea.

Both the PCP&C and OCZ are great brands. I'd say the OCZ is 99% rock stable, while the PCP&C is 99.9% rock stable. But the PCP&C is a better solution for using SLI, so that's why I recommended the PCP&C one over the OCZ one, since you plan on getting another 7800GTX in the future.

ill probably need more than 300gb.ive got 200gb at the mo and thats 95% full. so ill probably need about 400 to keep e going for a while.
what about the WD caviar SE 16mb or the samsung spinpoint p hard drives? are they good?
is RAID0 really that unstable? what could actually happen to the data? will it get lost and be unretrievable? will the HDs break?
ordered a PCP&C turbo-cool SLi 510 yesterday, woohoo!
do you think i should change my RAM? i heard that the A64 memory controller can only run two memory modules at 1T timings. Any more and performance drops to 2T.i have 4 x 512mb modules

never, NEVER buy ATI for anything having to do with 3D Modeling/Animation applications. Not only do Nvidia cards get along much better with these applications (LW,Maya,3DSMAX) but perform around 33-50 percent better as far as viewport performance goes. I tried a 9800 Pro after using a GF4 4600 and i quickly learned to hate that damn card.