I have to disagree.
The only difference between the B20 block and a B18B Block is the bore. (and in some cases the pistons, but its higher compression so thats a good thing not bad).
The cylinder walls are quite thin, so if you plan on boosting or really high reving, resleaving is not a terrible idea. However, there are plenty of people out there with stock sleeves running impressive B20/vtec builds.
You can basicly do anything to a B20. With out taking the vtec route, like the B18B you are going to be limited to streetability. Since you will not have a lower cam profile, if you want real power you are going to have to deal with rough/lopey idling.
It is very possible to get over 200whp NA out of a non-vtec B20. Its all in building it properly though.