I've never really felt the need to spend big on brake discs, I would feel pretty comfortable in buying cheaper ones.
I would however wait until you need pads, then replace the rotors. I would run the old pads on new rotors, I'm sure the rotors will be fine until new pads are required, unless you are seriously under the min spec on the discs, like 1 mm under the min, then I would start worrying about how far the pistons are stick out of their bore.

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