Thoughts are wonderful, but here is some knowledge and experience.
Lightroom is a very CPU intensive program, the more cores you can throw at it the better, and the faster those cores are, the better.
In all process an i7 will out perform an i5 and an i3 will not be enough unless your doing quite low volumes of work, or still using an 8-10MP camera with no plans to upgrade.
An i5 is often sufficient if your not a heavy Lightroom user. LR does not use the hyper threading for exports, preview renders and most adjustments.
It does however use it for the local adjustments. With hyper threading disabled local adjustments on 5D2 raw files become very slow and unusable at larger brush sizes, but are smooth and easy to use with it enabled.
If you have the space in your budget, get an i7 3770.
It will also help future proof your system against the ever increasing files sizes from new cameras and any advances in Lightroom.
An SSD is nice. I have 2 of them. They do not however make a dramatic difference to LR performance.
Everything loads faster, and anything using the catalog is more responsive, but you need to keep all your images on as well to really experience a big difference.
If you get one, put your catalog on it, and of course remember to back it up.
The SSD has made a dramatic difference to boot times and program load times.
8GB of ram is enough for 99% of LR tasks. 16GB is nice, again for future proofing and if your also going to do some heavy work in Photoshop or other intensive programs.
Graphics cards, as you've pointed out, have no impact on Lightroom performance, and the on board Intel HD4000 is more than enough for Photoshop.
Photoshop makes limited use of open GL, which any current GPU supports, it does not matter if the card is AMD/ATi or Nvidia or Intel.
If you get into Video then things change, different programs use different technologies to speed up render times. An AMD/ATi card will do nothing if your using Premier pro, it is only able to make use of Nvidia cards, and only supports a limited number of cards unless you modify a settings file.
Meanderthal, it looks like you've done your homework and your suggested list would be a great build.
The only thing I would add would be an aftermarket CPU cooler, does not need to be anything fancy, but Intel have really skimped on the cooler size for the i5s and i7s.
It is sufficient, rather than being best. With the stock cooler on my first i7 I was seeing some quite large temp increases when using LR, my $60 aftermarket cooler (a coolermaster something) holds a constant temp even when running at 100% for 3 hours while rendering video.