Have you tried any of this in the config.ini?
1) reduce sound settings to minimum. See [sound] section. Much of this section identical to old IL=2. Turn off the radiochatter, reduce channels...etc.
2) force to run on both cores by setting processaffinitymask=3. make sure the semicolon in front is removed or it will be ignored.
3) lower dynamiclights=0, read this had good results on SimHQ forum.
4) lower other settings (e.g., water=0, effects=0, roads=0, landgeom=2 or less...etc.)
5)also could check your graphics card GUI and for now make the settings as high performance/flexible as possible to get the game to run, then adust the up later.
6) I also wonder about texture compression. If there is a setting for this or not? I don't know. In your case, you would want it on to free up some RAM.
ps - i don't have the game yet. but my system is mid-low too. so a little worried
