Pretty easy to turbo a 2.5 RS, but you might as well turbocharge your Cav. It would be cheaper than buying an RS and then turbocharging it. If you're just looking for daily-driver power, the turbocharged Cavalier will be just as worthy, too.
www.twistecproducts.com can hook you up with a good turbo setup for your Cavalier.
If you're set on buying an RS and turbocharging it, go to NASIOC (
www.nasioc.com) and do a search in the "2.5 Liter Technical" section.