What sort of budget? The Really Right Stuff BH-40 is an excellent mid-sized ballhead, but not cheap, and you'll need an Arca-Swiss type plate for your camera (which is a better clamping system than the Giottos one, anyway).
The Manfrotto 468MG is also a great option, a bit less expensive, I'd pair it with a Wimberley C-12 clamp and a Wimberley P-5 camera plate.