Go for a decent intercooler, ported head and cam and you rebuild the CVH with a decent chip you will have a reliable 200bhp.

The prices quoted for the ZVH in reality are for a engine which will still be limited by the management used if standard and not perform as expected unless you have a good ported CVH head anyway.

I hope nobody here is going to suggest that a standard non heavily ported CVH head flows as much as the standard 16v head you are going to take off.
Why do you think all the people with ST170 heads are not throwing them away to put CVH heads on them ??