From my calculation I should be able to get upto 49kmph with a 120 cadence, and 45kmph with a 110 cadence with existing gearing. I think that is enough fro a recreational/touring bike. Downhills I guess I will not be hammering like on a road bike.
Got this from a BF post
Basically, gear inches x .2973 = your speed at 100 rpm. (roughly)