I would (unfortunately) have to agree with PMQ on the ram. I basically stated the same thing earlier, but I think he elaborated a bit and made the point more clearly. DDR2 will continue to get more expensive and DDR3 will drop in price. If you ever need to upgrade or replace something in the future, it will almost definitely be cheaper if you have components that support DDR3.
As far as the processor goes, I would probably take the i5 over the AMD 955/965, but that is a very close call. I would definitely take an i7 over the 1055/1090. For the record, that is not me being a fanboy. My first few builds were exclusively AMD since I couldn't justify the price of going intel. However, the performance of the current intels is worth any cost differential IMO (especially considering the cost is fairly similar). Then again, part of that might be my ability to obtain the i7 860 or 930 for $200. Even at $130 for the AMD 1055 (which is a pretty stellar deal), I'd probably spend my money on the i7 930 for $70 more. But, if you follow my spending habits I tend to throw money at stuff I don't necessarily need. If you're looking for a good read, check out this review:
http://www.anandtech.com/show/3674/amds ... t-reviewed
I love anandtech. That site has a way of explaining things so that even I can understand them. I'm no computer genius by any means, but even as a simpleton enthusiast it tends to make some sense. You can see some of the performance benchmarks there as well. I'll admit that benchmarks don't mean everything, but they can be a decent indicator of capabilities.
As far as the video card goes, I'll have to step aside and let others give advice on the ATI cards. I've never used one. All my PCs have utilized Nvidia cards, but a lot of that has to do with the fact that they tend to play nicer with Linux (which is useful to me, but I'm in the minority here). For a long time Nvidia dominated the gpu market, but things have changed slightly over the past year or so. ATI has put out some excellent cards (again, based on reviews and not first-hand experience).
Any way you slice it, though, this desktop will destroy your laptop for what you are planning on using it for. I don't think you'll be disappointed with any of these options.