The least powerful(And in this case;Lease expensive) 3GB AMD card i could find was the
r9 280 which is leaps and bounds above the 750Ti,but its also +$50 more.
Before you go spending hundreds on hardware though,we should know the rest of your specs.
It could be a waste if your processor is weak and old.. and its likely that anything better than a 750ti wont work without a new Powersupply if you're using a stock 400watt PSU.