I'd say my cheapest best mod to date is my OEM Si swaybar I bought for my '00 DX Coupe. It did my car wonders for handling and cornering, and only set me back $45 for the bar which I bought off a friend selling his (end links INCLUDED) and then shelled out another $18 for the pair of mounting brackets for it from the local Honda Dealership. Not a bad investment for only a little over $60.
