I've tried the INVECS-2 (2004 Lancer 1.3, 2000 Galant 2.0), found it to be horrible. If it's the same in the EX then avoid at all costs. Better have a test drive though or just get a manual gear (more fun, better fuel economy, etc...)
I don't think you'll feel any noticeable difference in the power between the 2007 1.6 engine and the 2008 1.5 one, as it's only a matter of a few BHPs and the new engine has better technology. Also the EX looks like it has better aerodynamics.
Do not compare the Lancer GT 2.0 with the 1.5. The GT 2.0 has almost 50 more BHPs and an F1-style (paddle shift) gear box :)