I've never seen an EC 130 used for SAR. i know Travis county used 135's for rescue, but have since moved on to the 145. as far as power, the EC 135 is a bit lacking, even being a twin engine.
I guess it depends on your crew, gear etc. Personally (being a nurse, and not a pilot) i would suggest at the very minimum a 135. This is just from hearing the pilots reactions to the lack of power in the 135. i couldn't imagine what they would have to say about a single engine aircraft, for multiple reasons.
Is this for high or low elevation rescue?