I do agree with you on the professional looks of a case. I'd just try to find something that fits your taste, is made out of aluminum and uses 120mm fans. Also I'd highly suggest a removable motherboard tray since you want to keep it at a mid-tower. I know I've cut my hands plenty working in smaller cases due to the lack of room.
I forgot Intel slashed prices last week. The price isn't too much more, like you said. If you are comfortable with overclocking then you can save some bucks and go that route. I've never had any serious, non-correctable issues from OCing, though that's just me. Depending on how much of an overclock comes into play the cooling solution though. From what I remember, the E8xxx are very nice overclockers even on the stock coolers.
That particular motherboard only supports DDR3. The 780i supports only DDR2. Beyond that I'm not familiar with the differences. I still don't think DDR3 provides another of an advantage for the cost. By the time it does, you'll probably be upgrading again.
PCI-E 2.0, at least didn't make much of a difference with the last generation of cards, but is standard at least on higher-binned X38, X48 and P45 motherboards as well. Just make sure whatever you get runs both cards at the full 16x, as that will make a bigger difference than PCI-E/PCI-E 2.0. Definitely make sure they don't run at 16x/4x.
Still just get the beefiest card you think you'll need and go from there. On the nVidia side eVGA is probably the hands down choice. Step-up plus lifetime warranty is fantastic. You could try out the GTX 260 and if it doesn't work then grab a GTX 280 within 90 days. Then down the road add another GTX 280 for less than MSRP now and be done with it.
On the ATi side, well no stepups or anything but Visiontek seems to be one of the only companies with lifetime warranty.
I don't have any experience with 64bit and more than 4GB of RAM. I know that 32 bit will only report something like 3.5GB. I don't know much of the particulars. If you get a retail copy then you get both, if you get an upgrade I think you can purchase the disc for 64bit for a couple bucks and OEM you might be stuck. Although I think I've heard that the licenses works for either...as long as you have the disc from somewhere.
I forgot to mention about that monitor...I've heard a lot of problems of it being loud. I have no idea why and no experience with it. It does use the same panel technology as my LG, which is fantastic for gaming and colors. It's a very good in between TN and IPS.
Western Digital warranties their Raptors for 5 years. I suspect the highest cause of their failure is lack of cooling. They do run a bit louder and a big heater than normal drives. Although when I ran 2 in RAID 0, it was lightning quick and I couldn't hear them over my ~70CFM 120mm fans.
All and all, your budget does allow you build quite a machine. The monitor will eat a big chunk of it but still parts are cheaper these days than a couple years ago.
