LMAO (I really did) Asus and stable should NOT be used in the same sentance!
If you are looking to upgrade the system over time you should start with the things that can be upgraded to a high spec system.
SO you need to start all over again. (sorry)
First of all, Pro video editing systems (high end) will use two or more processors, not dual core but two seperate ones. so that means that you are now looking for a dual processor board - Dont worry they do work with a single processor (that's the upgrade part of it)
You will need to get a Dual core Xeon processor, they are better at data crunching and have a 8MB Cache. I would leave this to last and get the best you can buy, the prices will drop on them and then a matching upgrade will be less.
for hard drives I would go for the 2500JS drives, they are sata2 but have a great continual data rate. you may want to check that.
If your budget on HDD's is fairly low, then get some smaller drives hitachi KS ones are good. RAID 0 the drives, and but a large single back up or two as singel drives that are not RAID'd
The RAM that you have selected, like Value have poor responce times, latacy will slow the workflow down as most of the procced data resides in the RAM and therefore the slower the RAM the slower the system. Idea RAM size would be 4 GIG but 2 is OK, you can always add to it.
the P180 case isnt the best, It looks nice but isnt practical, the wiring is hard and impossible as the PSU location is different and requires a long feed route to get to where it should be. - the P160 is nice, it looks better in real life than in photos and runs nice and cool.
I would head towards a full tower case or a RACK mount so you can hide it in a closet or some where else.
If you are not a gamer then you really dont need a graphics card. You can buy a low end card and there will be no difference, the 6600 VIVO will give you more than you need.
The main option for video editing card is the Agein physx card for anime/SFX productions these are stand alone graphic rendering processors which pop into the PCI -E slots
Gaming cards such as you mention are out put cards not control cards, you should be looking at the fireGL or quadro cards or even a matrox.
Hope that helps
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