Actually a notebook is a pretty poor choice for most of the software you have listed. You need a desktop computer optimized for graphics. You need a monitor that can show true color. For vue and Z brush you need as much ram as you can stuff in the machine and a MOBO/processor with a fast pipeline or you will have very slow rendering speeds. You also need a large and fast hard drive to access graphics files. For modeling software a notebook may not work well because the keyboard layout may be not standard and you use a lot of keyboard shortcuts. And again if you are doing any internal rendering a notebook just doesn't have the pipes to do it.
The video card is not critical, you are creating games not playing them, but some of them are optimized for graphics. It must show true color.
The needs for A7 are actually pretty low. You can design on any computer.... until you build a large level. Then if your computer can't crunch numbers you will be building for a looong time. If you are using a laptop make sure its plugged in, you don't want to shut down half way through a build!
So good hardware for graphics would be: Intel core 2 processors (extreme if possible) a stable MOBO with fast bridges, 4gb ram (more if you can find a stable MOBO), a fast hard drive (pick your poison), a good monitor (samsung or vuesonic..Eizo if you have the cash)A good video card with as much on board memory as possible (cause you know you want to play COD4!). and a power supply backup! This is just a home build, graphics houses have this as a workstation and then a central server to do the rendering.
Of course you may be able to work on a laptop. usually most mainstream graphics oriented laptops will just take longer to render and build. I had one once that used to shut down half way through a render. Obviously not a useful computer. If you are just doing some low rez images and low poly models it shouldn't make much difference. If you are going to use the software you have listed to its full potential and you try to do it with slow equipment you are asking for headaches.
