I absolutely need to replace my current electric toothbrush, and I'd like to find one with the best value, especially with compatible, quality heads. Which one should I take?

I have some discounts on OralB toothbrushes: Series 9, Series 6, or Series 2.

I absolutely need to replace my current electric toothbrush, and I'd like to find one with the best value, especially with compatible, quality heads.

Which one do you recommend?