Dont get the 3.6R if you want to match the mpg of your 2.5. It wont happen. I get about 18-22 depending how hard I drive but I did manage 29mpg once on a trip to Mass.
Its not super fast but it moves well. The engine and cabin are still quiet after 3 years of ownership. I do wish 3.6 had more of the engine tech updates that were currently available in 2010 like direct injection. But thats really it. Its a good car. I'm at 25k now and I'll definitely be keeping it for another 3 years at this rate.