You can slightly tune up or down your strings to see if it responds better to more or less tension.
There are not many synthetic core strings around.
Apart from the Obs, there are the Thomastik Dominants, Super-Sensitive Sensicores, Innovations (
http://www.innovationstrings.com) and some Velvet sets, although I know very little about them.
With steel strings, you have Pirastro Flatchromesteels, Pirastro Permanents, Corellis in tungsten and nickel sets, Thomastik Superflexibles (blue ends), Kolstein Varicors.
As you can see there are several choices.