A 305 or 315 tire will probably be cheaper than a 345. Generally speaking, 17-20" wheels in widths maxing out around 305-315 will generally be cheaper than tires falling outside that range.
As far as finding matching front and rear wheel with the correct or close offsets, you're right in that it is a complete PITA! I found a 10th Anniversary Cobra style 17x10.5, Mustang rear wheel from American Muscle that fits a Nitto 555 G2 315/35ZR17 that is dimensionally similar to my stock rear (with the exception that its Offset is 28mm, centering the wheel about 1.5" to the left of the stock wheel) and that I feel looks similar to my stock 2015 Base wheels, but most of the time it seems I find a rear wheel in a size I like, but the front wheels are wider than I'd prefer to use.
Since the stock front wheel offset is 42mm, you should be able to use any Offset that doesn't exceed 42mm. Keep in mind though, that some oweners run 3 rear wheels, meaning an offset up to 45mm will fit.