This is an argument that will never have a final answer but, yes 135 psi is enough to clean carpets, more is better but most people will not go much higher than 300-400 psi even though their machines are capable of much more.
Upholstery can be cleaned with a pressure of as low as 50psi, although again it depends upon the hand tool you are using as well as the size of the jets on the tool and the vacuums on your machine.
For upholstery one of the best tools on the market is the Dri-master 2 which leaves suites near enough dry when finished. As it happens we have two and I've just put one for sale on the "For Sale" section
