I would just stick with a pair of oscars in the long run, nothing else. Silver dollars should be in a group of 8+, anything less and they start to act differently. I've tried them, but they made my oscar too skittish, always bolting when someone walked by the tank or a water change was done.
Silver Dollars are weird. My three Tiger SD/s are jumpy in a 125 with my Geos, but the three Thin Bars in a different 125 in the same room, are super chill and never freak out.