The car won't die from using wheels that weigh half a kilo more. I'd be far more concerned about the tyres you're using.
Standard 172 wheels weigh about 4 ton haha
16" Turinis are 8.4kg
I would go for 15's anyway, smaller (usually) lighter and cheaper tyres.
Team Dynamics Pro Race 1.2's are 6.9kg in 15" size, might be able to find some cheap.
Unsprung...