You only need camber kits if you want to/need to bring camber back to spec, or adjust camber to a specific amount. Rear camber adjustment is possible with the stock components, but front camber is not adjustable with the stock upper control arm. A lot of people who lower their cars do not install camber kits. The induced negative camber with lowering +/- using spacers may cause uneven wear on the tires. However, the negative camber has other pros and cons to handling, depending on what you want for your vehicle. So, in short, aftermarket camber kits are not mandatory...depends on your application.
I have SPC front and rear camber kits because I wanted to corner balance (you can only corner balance with coilovers, btw) and specifically adjust my suspension for an aggressive street/occasional track set-up. After installing coilovers and lowering my car 0.75" front and 0.5" rear, with 15mm and 20mm spacers, my front camber was way off. I needed camber kits to dial in the camber to -2.2F and -2.0R. This front camber has greatly reduced understeer for me. Tire wear has been pretty even thus far.
Your 20mm and 25mm spacers with the 19" Rays will look great after you install your Eibach springs.
