Fascinating, pragmatic way of looking at student body quality - I wonder where you could find this sort of info online?
Ruggs lists recommended
departments for colleges.
UIUC - 47 departments mentioned
UIC - 31
SIUC - 25
NIU - 20
EIU - 16
WIU - 16
ISU - 6
SIUE - 5
For what it's worth, which may not be much

for instance, I would have placed ISU ahead of NIU/EIU/WIU based on average ACT scores.
My niece went to Western, where she obtained an accounting internship with the state, so even average 'directional' schools offer some advantages.
Northern is mentioned in other threads on this board - search for "NIU". I'd be worried about the 'suitcase school' aspect, personally, unless you plan to leave campus every weekend too.
The student body varies at these schools. UIC is going to have a lot of Chicagoans and suburb commuters, for example, while the downstate schools will have many suburb kids as well as downstate kids.