mate you wont be let down by a b20 they are awesome and suprisingly quick engines, ive been rocking mine for over 5 years.
but as you know it is not as simple as buying a cheap block, you will need to change alot of stuff.
the vtec cross over can be violent depending on your cams i would recomend ek9 or dc2 cams.
here is some important stuff you will need that is often over looked.
you will need a catch tank set up as the b20 block vents through to the cylinder head and the vtec heads cant vent the pressure, b20 blocks dont have the charcoal canister.
there is a test peice you can get from honda(lings) that screws in the block where the charcoal canister does go
a set of arp head studs, as the heads have been known to blow off the block
and i would change oil and water pumps as the engine will be operating at higher rpms, dc2 ones fit well.
any Q's drop me a pm
hope this helps you out