The stock 0.9 bar cap should be just fine for 99% of people out there. As far as reliability and higher pressure caps, both my Eclipse and my
MR2 have had 1.3 bar caps on them for many years (7 years on the Eclipse and 9 years on the MR2). MR2 guys report that the 1.5 bar caps present no problems as well. Other than the caps, my cooling systems are stock. So, it's probably not going to hurt...