tire width change vs car performance?

[motex]

Hey guys,
Im switching from 19" to 20" wheels but my concern is about how much the extra width of the tires will affect my first acceleration ? for sure it takes more effort to move those tires.....
Remember I'm going from 255-50-19's all around to 275-40-20's on the fronts and 315-35-20's on the rears, that's a lot of extra rubber touching the ground......
One interesting proposal I received from the tire dealer is to go 295-40-20's all around ? even with stagered wheels since that size will fit on 9.5" or 10.5" wheels, the only issue is that probably the rear ones could look a little "short" on those wide wheels
Well, hope someone here will be able to send me some comments
Bernie