Add some ram to your existing LT and maybe a larger hard drive...
But as much ram as you can afford and you should be fine, plenty of desktops still runing 16, 32 abd 62 negs out there which do more than fine painting the GUI and various other skinnables....
if your bound and determined to get a new one, check whom you bought the one you have now and see if they have an upgrade deal, or if money isn't an issue and your into the thought of high end toys, Ti 17, i-Go, Sharp 3D (yes it is true 3D without the glasses or other head gear), IBM if you also use it for work....
Others will come up with and might even bitch about one, a couple or all of those I have mentioned, but so what.
Personally, I have IBM laptops and they work fantastic both with doing graphics and under their alter egos of Administrative systems and tech systems...
i-Go is the toy I am leaning towards in the future..