Ram isn't super expensive anymore so I would go for 6 gigs or more. I'm biased because I hate carrying a laptop that's bigger than 13 inches so I would rather give up performance for size. You can always plug in a monitor. I prefer laptops with no cd drives as that helps with the weight and thickness. I'm out of the loop with CPU and video card specs so if I post something underpowered I apologize. Copy and paste the chip model into google to see benchmarks.
Vostro 3360 Laptop Details (customizable)
Samsung NP530U4C-S02CA Intel Core i5 3317M 6GB 1TB 14in GT620M DVDRW WLAN Win7 HP Ultrabook 799 (i know its over your budget)
ASUS Vivobook S400CA-RH51T Intel Core i5 3317U 4GB 500GB 24GB SSD 14.1IN Windows 8 Touch Ultrabook 699