jakemarietta,
I would definitely try to step up to the 265/35R18 for the front. You will be very happy with this setup. It will give you just enough understeer to inspire confidence. If the 265 won't fit on the front wheel (given the offset), I would step down to a 265/35 rear and up to a 255/35 front. A 30mm differential from front to rear tires on a NA will give you a lot of understeer. If I'm not mistaken, they NA has the same size tire front and rear from the factory.
Steve,
I would probably keep the 235/45R17 up front and add a 265/40R17 in the rear. This should optimize the available wheel widths (I know you can go wider, but it's not optimal). Keep in mind that a wider tire is not going to increase your straight line traction (remember it's all about car weight, tire pressure and tread design when it comes to the total size of your contact patch). The wider tire will give you more longitudinal grip (great for corners). I would then add a TRD 27% stiffer rear swaybar to balance the handling. The rear bar may not be perfect, but it would get you close enough that you could use tire pressures to fine tune the balance. A swaybar is a whole lot cheaper than a wider set of wheels.
Later, Steve