I have schwalbe Marathon Tyres which I am happy with, so looking at the advice I will stick with them.
I might experiment a little with the tyre pressures though looking at Dans post.
Schwalbe Marathon are quite a good tyre, but there are others in the same 700C x 32 size that roll better.
Continental Grand Prix 5000 is supposed to be very free rolling, while retaining a degree of puncture resistance, but would be more fragile than your current tyres. I reckon I would be OK with these with a lightly loaded bike on good road surfaces, they are rated better, for both rolling resistance and puncture resistance, than the Schwalbe Ones I currently have on my old derailleur bike.
While a lot heavier than the Continental Grand Prix 5000, the Schwalbe Marathon Supreme is significantly lighter than the standard Marathon, with less rolling resistance and (in my experience in other sizes) good puncture resistance and durability. I have Supremes on several bikes, but in fatter sizes than 700C x 32. I noticed the improvement in comfort and rolling resistance when going from standard Marathons to Supremes on my old utility bike (650B x 42).