For June I see DC-9s and ARJs on NW between MEM and ORD (don't see any A320s). Limited to 69 seats, the ARJ is very popular with FT'ers for the added space and legroom.

Know you don't like CRJs, but NW has now started CRJ service between MDW and MEM. MDW fares are normally much better, so if that option works for you.......

Any option you choose, will always be better than driving......