Personally, I feel that if you are not going to be gaming, I wouldn't spend the extra on a PCI-e. You could build a really nice budget machine when you don't have to worry too much about gaming. Your set up looked nice. I'd go ahead and get 1gig of ram as it can never hurt if you use things like photoshop, etc.
Lian-Li is a great case, no doubt about that, but it is a pricey one. There is no problem in this, but this would be an area if you needed to cut cost, you could. The sonata also comes with a nice Power Supply that you could use.
Main thing you would need to change would be the motherboard, video card for the pci-e set up.