I hate to say it... but most pcbs are junk at this point as mame emulates them prefectly... and I mean perfectly. Once the games are booted up and running, even a collector would have a hard time telling the original apart from the mame cab. This is only 90% of the time though. There are some games in mame that still have problems and there are some games that use special hardware devices (knockers, lights, force feedback, ect...) that mame doesn't yet support. And the random incomplete driver, ect...
As a whole though I can't agree with you peale.... mame is just like the pcb, assuming it's running on the same hardware. (True arcade monitor, no stretch, ect...) the only difference is, the pc is at least 10 years old, unreliable, and takes up enough space and power to make it akward enough that collecting multiple pcbs isn't a playable solution unless you have a cabinet for each one to go in.
Of course unemulated games/systems are a different story.
Also if you have a unmodified arcade machine with a working pcb in it.... maming it would be silly, but that's just my opinion.
I recently finished my gorf conversion after getting sick of throwing all my time/money at getting the original pcbs to work. Although it bothered me at first, in the end, having a machine that can play gorf, the three games that "inspired" gorf and a slew of other verticals is way better than spending $150++ to buy a new rack set that would probably fail too considering how unreliable the midway rack system was.
I would like to point out that it's a true conversion though, not a butcher job. The cp was unmodified, I didn't add a million extra buttons or cut up the cabinet or any of those unspeakable acts. there are no holes in the cab for power buttons or any visible alterations what-so-ever. The only difference is now instead of an arcade power supply and a gorf pcb rack the machine contains a pc motherboard and a pc powersupply.
(Well, I also threw out the orginal wiring harness, but that was because someone tried to "fix" it before I got ahold of it and ruined it... probably what screwed up the board too.)
When a conversion is done like that, I really can't see how an original pcb even compares to mame running said game. The only benefit I can see to running an original pcb is a faster "boot time" other than that a computer has all the advantages.
With that being said, I don't mame working cabs even if mame would add more functionality. Finding an original cab, with the original pcb in it working is like a gift from heaven. Don't mess with a miracle.

So does anyone need n.o.s. rgb filter, audio amp and various other parts from a gorf machine?

Sorry to get off topic.... just thought I'd throw in my 2 cents.