I think your best bet would be to stick to Wynnefield Heights (section near Conshohocken Ave & Country Club Rd), Balwynne Park, Belmont Village (an often overlooked neighborhood with some interesting architecture and mix of neighbors), City Ave. areas of Wynnefield and Overbrook if you're looking to buy or rent. Sections of Wynnefield below Wynnefield Ave. aren't as stable.

Overbrook Farms is probably the most elegant of Philadelphia City Ave neighborhoods, but it is at a higher price point than all the other neighborhoods mentioned.