MBox Pro 3rd Generation Computer Question, Custom built or Dell?

[Stratoblaster]

I am going to purchase a new MBox Pro (3rd Generation), and a new computer. I have been trying to figure out the best PC to purchase, to use my new 3rd gen - Avid Mbox Pro on. Right now I am using an MBox 2 with a Dell XPS 400, Pentium D (Windows XP Pro).

I am wondering what computer will work the best with the new MBox Pro? I have been looking at the new Dell XPS 8300 - Windows 7, with the new i7 Sandy Bridge 2600 processor with 8 GB of ram. With dual hard drives (estimated cost $1300)

or,

The Sweetwater Creation Station i5 - 64 bit, with two Seagate 500 GB hard drives, Windows 7, and 4 GB of audio grade ram. cost $1549.99 with shipping

or,

The Quad Pro from ADK (ADK Pro Audio) with Windows 7, the new i7 Sandy Bridge. Two Seagate 500 GB hard drives, 4 GB Mushkin Ram, ATI Dual head fanless graphics cards 512 MB. Cost $1661.00

I would really like to buy the Dell XPS 8300 with the i7 Sandy Bridge processor, because it is cheaper and I can get more RAM, a better video card, and it has the newest i7 processor.

I am wondering though, which PC would be the best fit for the new Avid Mbox pro with firewire? Do I really need to spend the $1549 from Sweetwater or the $1661 from ADK to get a good stable system for recording? Any help or suggestions please?