I'm with Silvune here. His hard drive and RAM recommendations are spot on. I was about to post the exact same thing until I hit the "refresh" button and noticed Silvune had it covered.
The drives mentioned above are considerably faster due to much higher data density. The old WD 500GB drive in your original post uses 250GB platters. The drives above use a single 500GB platter. The higher data density makes them much faster. The fact that they're cheaper is icing on the cake! I would stick with the Samsung drive.
Edit: I'm not crazy about ASRock boards. Here's a very nice Gigabyte board in a combo deal that makes it only $15 more than the ASRock board.
I don't plan on using crossfire right away since I only plan on buying one GPU. However, the PSU is "crossfire ready". Does that mean I have to buy additional hardware when I wish to use two video cards?
Also, I'm wondering whether or not I will need a 650W PSU, even if I want to OC later...
Finally, thanks for the HD and RAM suggestions.
Is there anything specific about why you don't like ASRock boards? Or is it more of a brand thing?
It's a reliability issue. Gigabyte boards use higher quality components. ASRock is just the budget division of Asus. The boards are OK, but if you can get an Asus or Gigabyte board for about the same price I'd do it in a heartbeat.
The 650TX is a quality PSU that could technically power Crossfire 5850 cards, but you would be pushing it a little. It also doesn't have enough power connectors, so you would have to use power adapters. Your GPU comes with the adapters, I'm just not a fan of using them. I figure if the PSU was meant to power cards that require four PCI-E power connectors, they would have put four PCI-E power connectors on it. You're better off with a 750W PSU if you're trying to plan for Crossfire in the future.
And if you don't use/have the adapters (or could not otherwise get them) then you would have to buy a new powersupply when you wanted to crossfire, which would be a waste, especially if you could have gotten just one that would have been able to do it the first time around.
650W PSUs are actually probably the sweet spot for dual 5850s, apart from the power connector issue. Guess I would say the power supply makers are behind the times. Only because it takes longer for them to adapt to the power requirements of new components.
Tbh I think you're better off keeping your build with some of our suggestions. Because the PSU is from Rosewill who aren't really known for making quality PSUs, the HDD looks slow and the RAM isn't quite as good with CAS9.
I will weigh into the Mobo discussion by saying that I don't think that there would be any problems getting an Asrock board.
Are you having budget problems or something?
If you wanted a PSU that could handle crossfire (without adapters) then this has to be a contender: Antec TruePower New TP-750 ATX12V V2.3 / EPS12V V2.91 SLI Certified CrossFire Ready 80 PLUS BRONZE Certified Active PFC $125
I'm not impressed with that combo. In fact, it doesn't even make any sense. They've paired a motherboard with video output with a CPU that doesn't have an integrated GPU. You would have to buy a GPU for that build.
It's also always a good idea to avoid Rosewill PSU's. They have earned a reputation as being a sub-par PSU manufacturer. The PSU is the most important component to a stable system and not the place to use a questionable quality component.
The HD in that combo is a slow 5900RPM drive that's more suited to a HTPC, not as a main system drive.
Well there are a number of factors. The components you are going to use, primarily the CPU and GPU(s), you have to know how much power these will use. Then how many connectors the card needs for that. In the case of the 5850, two 6pins each. Then the PSU has to be of a good quality, which you can either go by the reputation of the brand or look at professional reviews to know that it does what it says on the tin.
If you're going to OC the processor then you probably would want to buy an aftermarket heatsink. If not then the HAF 932 is one of the best aircoolers, so it will provide a nice cool environment for all your components.
You could save a bit on the case, by going for the HAF 922 (which is a massive mid tower and supposedly better at cooling than the 932), or perhaps the CM 690 II Advanced.
I would assume the same thing.