My advice is similar to the others get a DELL.
Just got my new DELL 8250 with a 19' flat panel monitor and all the other bells and whistles. Couldn't be happier with it.

As Andy suggests, look at their website. They run frequent specials which seem to change every 2 weeks. Upgrades, Extra memory, bigger hard drive, free shipping. It constantly changes.
For your purposes, You might not need to spend the extra $$$ and go with either a 2300 or 4500 series.

BTW if you don't want to see yourself selling that computer, stay away from the day trading