It seems that you are making a system that is tweaked more toward gaming, if so I would sugest that you do go for the 2500+ Barton, and go with a dual channel ram set up, 512 is fine, but 1 gig would be better. My friend got 1 gig of Corsair Ram for approx $160 at newegg, look for "CMX512A-2700C2P".
Evrything else seems to look, ok, but honestly I do not like they Thermaltake Volcano 11, they are a bit loud for my taste, I would go with an SLK 900U and a 92 mm Enermax speed controled fan, but that is only for the select few who can mount the bloody thing

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Good luck with this, and rember making the perfect comp is an art, you will never get it right, and it will not be appreciated untill way after its gone
Good luck to you, and do calculations for shipping. Some things may cost more, but when you add everything up in the end may end up saving you money on shipping, but can inconvience you if you have things coming in from five differen places. In the end you do the balacing, and see what you would perfer.