maybe he doesnt have enough $$$ to buy a bseries swap and do what he wants to do with the engine..... like me, i want a turbo-ed car.. i can get a d16 and build my own turbo kit for less $$$ that it would be to buy a stock b series swap, hence the reason why im not going B... if i had an extra 2 grand lying around, sure id buy a b16 and turbo that.. but im broke and out of a job until school ends so d series is fine for me..
dohc does have much more potential though, maybe look into getting a dohc zc.. close power rating as sohc but can hande a little more power... around the same price too, if u shop around...
but if ur sticking to sohc, def. get the y8 or a z6... id prefer z6.. you will be happier in the long run