Don't blame ya for ditching the PC monitor. It's like eating fat free ice cream. It'll do the trick if that's all ya got, but nothing beats the real thing!
Now, I don't have a real arcade monitor in my cab, and since I'm a yank don't know anything about the SCART set-ups, but I do use a 24" RCA TV in my cabinet. I've been playing on it since last Sept/Oct when I finished my cab, and have absolutely no complatints. It was cheap & easy to set-up, and is pretty close to classic arcade. Yeah, there are some drawbacks (vector games not so crisp, but still very good, also small print can be hard to read) but overall for the price & ease of installation I'm very satisfied with using a TV.
Unless you got some money burning a hole in your pocket or are a perfectionist, get the TV!