Make sure your RAM is compatible with the motherboard. It's very important when you run into 12GB. I have seen an i7 system with 12GB but the system only recognised 8GB and after some googling, it seems to be not that uncommon. Not sure about Gigabyte but Asus has a RAM compatbility list which tells you to the extent whether it will work with all 6 DIMMS slots filled. It's best to (1) get the RAM which the MB producer says will work in 12GB and/or (2) make sure somebody has the same combination working.
For GPU, go for a DDR3/GDDR3 at least regardless of whether you are going to play games or not. And DX11 is a plus, just to make sure it's relatively more "future-proof". It's not that much more expensive. Like my current Asus EAH5670 (ATI HD 5670 chip) with 1GB GDDR5 is only about $90 if I remember correctly. If you go for 512MB, it will be cheaper. A vid-editing machine is usually too fast to just use for video editing, IMO. A bit of light gaming here and there won't harm.
Drop the X58-UD3R . I'v used them (including the X58A and X58-UD3R) and they are OK (both have massive vdroop even with LLC, but that's not really important to OP), however, if you want something really stable I recommend a P6T-SE (I'm currently using a P6T Deluxe v2 with my i7 rig; see my sig for more info). http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Since you probably won't do a crazy OC, you don't really need the PI Blacks.
Don't worry too much about RAM. Most of the RAM compatibility issues are related to motherboard (another reason I don't recommend the X58x-UD3R). Beware, that when running any set of 6x2GB DIMMs you will probably need to increase RAM voltage a bit.
I find that the Antec 300 becomes quite crowded when you add HDDs down the road. It's more than likely you'll add more (I'd say, 3-4 with out OS HDD) HDDs to a vid/photo editing rig than a gaming rig.
As for the HDD set up I recommend this:
2x 500-640GB HDD for OS in RAID 0
2x 1TB Samsung F3s in RAID 1 for data.
This is the usual set up I do for people doing vid/photo editing,etc.
Since you arn't gaming: the 4550 ($20) http://www.newegg.com/Product/Product.aspx?Item=N82E168...
This should be fine, however, beware that depending on how complex your 3D work is, this card may lag when turning the model,etc. I can't really say how this will affect 3D modeling, however in CAD (SolidWorks & Inventor) a 4650 laggs some times; and no, this is NOT CPU lag(lol, happened on a 2P Nehalem).
Depending on your work, equipment (HD camcorder,etc) etc consider adding a Bluray burner.
@OP: Could you list your software? Maya, CS4,etc?
Other notes: Depending on how valuable your photos,etc are I recommend you burn them on to BD or DVD for backup (I do this for all finalized stuff, along with backing up on a NAS and backing up THE MOST important photos,files,etc online, it's well worth the extra money imo). I find that with external drives, you get some level of protection, but they are STILL HDDs. I may be a bit paranoid, but it sure beats having the pics,etc lost and trying to recover them (professional data recovery easily cost $500+; usually about $800+) in the event both the NAS and my external HDD dies.
Wanted the usb3.0 and that board got great reviews and looks pretty good for the future.
I'm going to keep the RAM i had selected because A) I wanted the CL of 7 so I'm gonna stick with the PI blacks and B) I'll never fill out that rebate form for the cheaper stuff
Switched out the case like you recommended, strong points there can't argue with that.
HDD: good idea on that setup but I don't have the money for that right now. I'm pretty set with my external for data right now so I think I'm going to stick with the
Western Digital Caviar Black WD6401AALS 640GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Changed out the GPU to that card you listed, not doing any 3D work so i should be all set there as long as the card can handle 1080p footage that's all that really matters
Might add a bluray drive in the future but not now.
I'll be doing all my work in CS4 so thats all i really care about functioning around.
Unless you have any more advice I'm going to order this set-up tomorrow sometime.