That's true but a 4890 is better than a GTX 260 and a 4890 is cheaper from what I've heard.
Western Digital Caviar Black or Samsung Spinpoint F3 for performance over that Seagate.
Western Digital Caviar Blue if you want something for reliability.
i7 860 vs i5 750 for gaming...
They perform about the same...
I don't think it's worth the $100 personally.
The motherboard's ok, but I would get something with Sata 6Gb/s and USB 3.0 for maximum upgrade ability.
And ultimately for gaming and upgrade ability, I'd probably get a cheap AM3 motherboard a Phenom II and an ATI card, but that's just me.
Intel vs ATI is a choice to be made by each consumer individually.
Your Power Supply choice...
Newegg.com - Antec EarthWatts EA650 650W Continuous Power ATX12V Ver.2.2 / EPS12V version 2.91 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC "compatible with Core i7/Core i5" Power Supply - Power Supplies
That Antec Earthwatts would do you just as good, and would save you $15
(DOA parts happen sometimes, don't be discouraged by the poster below, the Antec Earthwatts series PSUs are great.)
I like my wallet, and all the money in it personally.