Different brand tyres F/R?

So just wondering is it bad to run different brand tyres front/rear? Some people tell you will have 'tracking' problems etc.?
When I first bought the car it had different brands on the front and rear, but then again the tyres were all no good.
I'm getting some Federal 595 RS-Rs (140 treadwear :)) for the rear very soon but will have to use my cheap Chinese budget fronts till I can afford some new ones (most probably RS-Rs also).
Sizing is:
(F) 215/40/17
(R) 235/40/17
 
Thoughts?

Well I don't get any noticeable understeer at the moment, more sidewall roll more than anything. They're pretty cheap ~$100 fitted lol
 
I just thought since the sidewalls on the RS-Rs are meant to be pretty stiff, would it cause any handling problems? It's a daily driver and I wont be driving it 100% of the limit.
 
 
 

Lol well u won't have to worry about lift off oversteer. But under steer might be a bitch. Don't try any fast u turns.

Definitely will be getting a set of Federal RS-Rs on the front now. After that blast through the twisties on the weekend, the back end felt stuck down with glue no matter how much I gave it out of tight corners! These tyres are absolutely fantastic. Still yet to test them in the wet, but in the dry they never ever want to let go. The sidewalls seem a little on the soft side, but nothing major, still a much better feeling than anything else I've had on there (S-Drives,FK452s etc) and good ride quality and not much noise either.
front was a different story, as I was getting understeer pushing into fast corners whilst trying to stay in my lane.
 
These bad boys