$1000 Work build - help appreciated!

I started at a new job as a paraplanner (like a paralegal but for a financial planner) on Monday and I took on the responsibility of ordering my own computer. I need to keep it under/around $1000 including:

1. CPU - was thinking AMD 3800 X2 for price/perf.
2. MB - would like integrated video and quality reputation
3. RAM - 1gb
4. OS - XP Pro needed
5. LCD - Would like 20"+ Widescreen, 75hz+ (height adj. would be a plus)
6. Speaker - Could be part of monitor or attach to monitor (cheap is good)
7. Keyboard/Mouse - need ergonomic (I'm 6'5" with big hands)
8. HD - 160gb+ with good reputation
9. Case/PSU - something cheap with a good rep
10. Office 2007 - not needed, but I'd like it as the Excel 2007 could save me a lot of time since I'm mostly working with spreadsheets all day and Word 2007 doesn't suck (unlike previous versions).

I mostly use a PC to do spreadsheets, internet apps, client relationship management apps and emails. I really want a good monitor and at least a gig of ram while the rest doesn't matter much as long as it doesn't fail. I'd like to get Office 2007 if I could stay in my budget.

Should I use HP or Dell, or can I build this cheaper/better by myself or somewhere else? (I've done a few builds before but haven't in a while). I have to buy the OS, so that could make a difference on the price.

Thank you for all of your help! -Matt