For the same price get a Samsung F3 or Seagate 7200.12 1TB HDD. They are newer and faster.
Thats a ton of graphics power for that resolution. You could easily drop to a 5850 and realistically even a 5770 for 1440x900.
You didnt give the purpose of your build. If its for gaming then going to an i5 750 CPU and P55 motherboard will save you money and provide the same performance. If you do heavy computational tasks or video editing then the i7 930 (new replacement for the 920) may be the correct CPU for you.
All the new 5000 series cards can handle dual monitors easy. Keep the little one plugged in running your desktop for the wife to use and run your games on the new 24inch one. See how long she stays with the little one given the option.
I have never seen anyone say they bought a "lag reducing NIC" before. I have a hard time believing an overpriced network card can do much about problematic internet connections. Anyone ever use one? I suspect they are like add-on sound cards. Onboard is so close in quality that its pointless unless you are a musician doing production work on it.