I went with d15b single stage, and m totally satisfied with the results. Anyone who's looking for the difference between D15b single stage and 3 stage vtec,....
D15b 3 stage vtec : 60% economy, 40% power
D15b : 50% economy, 50% power
Thanks loads for your effort on replying :p, and yeah your post saying go for single stage, that made me do some research and i finally got the decission rite.