Hi Mazex, over several diff PC builds and related evaluations I concluded that with a duo core CPU wherein even when it did NOT show full CPU utilization a simple drop in of a quad core resulted in significant FPS increases and noticeable smoother gameplay for the IL-2 series.
Based on your data, your CPU was limiting despite the fact that you were not showing 90-100 core utilization. I suspect it has something to do with the architecture of the old DUO Cores. The 60% utilizations with spikes into the 70's apparently was in fact a bottleneck. I have experienced this on various PC builds for my personal use as well as paying customers.
Stepping from 275 to the 580/570 is also a huge step in throughput capacity - assuming you are not limitd by a duo core CPU. For example, if you dropped your 275 in your current rig, I would bet you a NEW SET OF TEETH that your FPS, fluidity, and pleasure will drop through the toilet. THEN you would be calling me to unclog with some new PC giblets. Try it please sir - just to confirm as many others are likely to find the results/conclusion useful, and that is how our community adds value to these forum posting/rants.
As a side note I bet this current version is not really the new engine they have been working on, it plays like the old engine with modified textures and other bits. Even some of the odd interactions between objects can be seen in CLOD as they were in the groundbreaking Orig Series.