Jerry:
It might just be that sometimes a move feels different, is more comfortable or works the muscle differently with a barbell.
I would get one if I were you. Next to dumbells, a barbell is the single most valuable piece of weight training equipment.
Walmart, Sears and Dicks all have amazing prices (from $19.99 upwards) on barbell sets, including 110 pound sets for less than $40, on their online stores. That's a pretty amazing deal.
Clare