Here's some coupons for the dell laptops, they change every week so if you find one you like, use the coupon codes
http://www.notebookreview.com/dellCoupon.asp
Keep in mind though that if you do use one of these coupons, it replaces whatever promotion they have on the site. For example, it the site says 100 dollars off instantly, and you use the 225 dollars off, its not like its adds on top of each other to make 325, it will just be 225.
I can't really comment on the whole comparison thing, but I bet a quick google search you can find benchmarks such as Radeon 2450 vs 8400.
But I do recommend getting the higher resolution screen, it does indeed look better.