If you could possibly tell a difference in performance by adding SS lines you would have to have the most screwed up brake system IN THE WORLD.
BUT if you are driving on a track in a very competitive way SS lines will out perform the standard brake lines by not failing.
I would rather have good quality (stock MB) lines than cheap after market SS lines any day!
As far as disks there are far less manufacturers than there are retail suppliers, you don't always need to spend top dollar to get good quality.
If a company backs their product they may be worth looking into.
Plus being that E-bay is the single largest retail outlet on the planit it is very inaccurate to say it is all cheap junk...
Good Luck on the disks...
Mike