1 - For arcade monitors, you basically have five decisions.
First - size
Second - resolution (or multi-res)
Third - analog or digital
Fourth - flat screen or curved 'traditional' screen
Fifth - brand and model
The analog or digital choice is really only needed with the multi-res. For a mame enviroment, I suggest only getting a digital. See -
http://forum.arcadecontrols.com/index.php?topic=64850.0I'd go with a Betson multi-res, namely the
http://www.betson.com/products/IMP-44-4070-RT http://forum.arcadecontrols.com/index.php?topic=65451.0. Avoid the Wells Gardner -
http://forum.arcadecontrols.com/index.php?topic=64564.0.
2 - I wouldn't think that this would need any more than a TV. I think that the cap kits and such that 'arcade monitors' 'need' is due to them being used in an arcade environment, meaning constantly on 24/7 (or a lot anyway), and in those conditions for years and years now. I'd bet a TV used like that would need caps and such, too. I highly doubt that a new monitor used in a mame cab wouldn't need (or benefit from) a cap kit for years and years. Not a consideration unless you are using a used arcade monitor.
3 - Some need transformers, but most new ones don't. Some plug right in (these don't need transformers), some have wires that you will need to provide voltage to (either with a transformer or not).
4 - These questions are not necessarily directly related.
First, the video cable - some have the 'typical' PC monitor plug (HDsub15) and will plug right in, others have pins on their circuit board that you will need to plug into. The betson I linked to has a typical monitor plug and will plug right into a PC video card.
Second, the video card - none NEED the ArcadeVGA, but it makes it SO MUCH easier and nicer. Without it, you will need extra software, configuring, and hassle. (FWIW - I'm using an ArcadeVGA.)
Third, it sounds as if you are confused about this - the resolution of the monitor (if it's 15kHz (CGA), 25 kHz (EGA), or 31kHz (VGA), or multi-res (15-31kHz auto detect), the cable it uses, and the video card are all interchangeable (assuming your video card can output the resolution (CGA, EGA, VGA) and you have configured it to do so).
5 - I THINK so. Not sure.
6 - What you mean is multi-sync. This is not mandatory, but will allow more games to be played, and a better looking FE/windows enviroment. Essentially, you want a monitor that will at least sync to 15kHz. This is what most arcade games used, and will give the authentic arcade picture. A multi-sync will run at 15kHz, along with other speeds, to give authentic arcade pictures for all games and will also give a higher resolution for windows. (It can be rather blocky... but is doable on a 15kHz only monitor). So IMO, either use a 15kHz (CGA) only monitor, or use a multi-res.
That Happ monitor linked - not sure about it.
Rick