you shouldn't have any problems installing both on the same PC.
matter of fact I have had several versions of sonar installed at one time with out any conflicts.
Sonar light IE- Sonar LE is basically a lighter version of X1 I believe.
Sonar professional and sonar LE are 2 totally different DAw's in framework.
share some features but mostly the same.
im a bit intrigued though by this theory you want LE because of its usage, because I thought if anything sonar Pro was better in almost every way.
even upgrades to SV.