$1000ish workhorse - What would you do?

[kuni]

APPROXIMATE PURCHASE DATE: Thanksgiving
BUDGET RANGE:$600-$1200, but willing to push it if it's going to be worth it.
SYSTEM USAGE FROM MOST TO LEAST IMPORTANT:Crunching massive spreadsheets in Excel 2007
PARTS NOT REQUIRED: Monitor, speakers, OS (if XP Pro is good enough)
PREFERRED WEBSITE(S) FOR PARTS:Newegg, anyone good and cheap.
COUNTRY OF ORIGIN:USA
PARTS PREFERENCES: None
OVERCLOCKING: No
SLI OR CROSSFIRE: No
MONITOR RESOLUTION: 1920x1200)
ADDITIONAL COMMENTS:I want the case to be easy to work on, quiet, well-built and decent looking. Nothing that looks like Megatron. Also, I've never built a system before.

I've been asking and I'm still trying to figure out what's going to make this machine a SCREAMER for Excel. Can XP or Excel use more than 2 or 3 gigs of ram? Will XP Professional hold me back from a huge Windows 7 speed and memory advantage? Should I get Ultimate? I'm all for overbuilding, but seeing as how this machine will have a single purpose, what's the sweet spot?

I know I could save a few hundred on an i5 system, but if a 920 will be *that* much better, I'm all for it. I ran my spreadsheet on a Core 2 Quad (2.66 8300) and it was half as fast as my Core 2 Duo (2.4). Weird.

Anyway, would love to see what you guys would do!

Thanks!

 

[kuni]

Been looking at this CPU comparo for help:
http://www.hardware.info/en-US/productdb/compareproducts/bGRkapiTmJXKY8g,bGhkapiZmJjKYMg,bGlka5iamJfKacg,bGlka5iamJfKaMg,bGZka5iYmJTKaMg,!/

 

[dndhatcher]

Look at this build. Inexpensive quad core Athlon for a really inexpensive build. Maybe with the sonata case as mentioned instead of the gaming case.
http://www.tomshardware.com/forum/274210-31-parts-homebuilt-bargain

I suspect windows 7 and 4gb RAM to allow more RAM and 64bit processing would help you (probably need the latest excel also). You could use task manager to look at your current memory usage before starting excel and after loading a massive spreadsheet to see how much RAM you really need.