hello there as you can tell by my avatar im an MSI fan did you want a desktop replacement or something more portable? because a 17 inch laptops like the GE70 are generally considered desktop replacements and 15 inch laptops like a GE60 are generally considered more portable now there is a GS series slim laptops but the problem in my opinion with slim laptops is that they generally have poor heat dissapation and cooling due to the fact that they are so slim theres not much room to work with, now with that in mind may i recommend the laptop i own?
http/www.newegg.com/Product/Product.aspx?Item=N82E16834152711
that one is the new 2015 model with the newest 9 series graphics card it has a steelseries back lit keyboard and can support up to 3 M.2 SSD's i dont think its very heavy at all but its not real lightweight like a GS series gaming laptop, now it is a little more than your budget but for a new model laptop with plenty of room for upgrades i think its your best bang for your buck
hope this helps would love to hear what you get sincerely a proud MSI owner