Is your car lowered at all?
For 215 widths, either 215/40/17, or the stock SVTF size - 215/45/17 will work as well.
The 40 series should be close enough to not have to worry about speedometer error.
45 will be a bit taller, and your speedo will read slower than actual speed.
i didn't install it myself, i had a shop do it. if you get your kit off of the tire rack, and use one of their recommended installers, said installer will give you $100 off. that's springs, shocks,struts, and alignment. personally, i paid $260 for the whole thing. the installation, that is. the kit cost $750. but it was well worth it!