I would recommend getting justy another 512 module for a few reasons. I doubt you need 1.5gb right now, like Wyodiver said it's hardly detectable in like 99% of circumstances. I would definatly stay away from 2 256's because that'll just take up more slots, and who knows how many dell gives you. For example if you have 3 and right now your using 1 with a 512mb stick, and you get 2 256's and ever do want that 1.5gb you'd have to throw them out and buy 2 512's or a 1gb stick. Also games like doom and EQ would probably benefit alot more by a better video card (what kind do you have?) than more ram, I run doom3 at 1024x768 at high detail with only 512 and it runs at 30-40fps steadily. Hopefully that helps.
