How to enhance performance?

[MiRai]

Why exactly do you recommend only 1 video card? Wouldnt 2 cards help on the performance? Lets say I open 2 WoW windows on each card. Wouldnt WoW run smoother on each client? And if so, should I go for the 570? or go for the 560?

This is a choice that's entirely up to you. If you want to deal with setting up multiple GPUs for each character set/game
client in World of Warcraft then go with two video cards. While the games might be smoother (all depends on which
settings you want to use), more components in the mix means more things that can go wrong and people who do use
multiple GPUs to split the load usually have lower end hardware or are running a ridiculous amount of game clients. In
my testing (and some other people as well), splitting the load in World of Warcraft between multiple GPUs could only
be done using DX9 and not DX11. So, immediately you're forced to play on dumbed down settings with your new shiny
video cards.

Also, what if you want to play a single player game or multibox another game that doesn't support splitting the load
between multiple GPUs? Now, what do you do? You're stuck with a much more inferior single card setup with less than
half of the memory of the GTX 580.

Another question, what will a SSD bring to the table? Im only looking for a smoother gameplay in crowded areas, less laggy arenas etc.

An SSD will only lessen loading times. Your FPS is still dependent on your CPU/GPU.