Dont' go composite, to crappy.
SVid is the best option in my mind.
http://www.xiaou2.homestead.com/turbo.htmlTake a look at the differences. This should answer all questions.
You can also go with a true arcade CRT using a jpac or hacked cable. But you will be stuck in dos and have to worry about killing the monitor until you get the configs right. You should get better output (ANYONE HAVE A DIGITAL CAMERA AND BOTH ARCADECRT / SVID TV?) but if you don't have the monitor, it will cost you!
So go svid and you wont be sorry.
btw, the trouble is usually finding a 25" since they are almost always 27". some 27" will fit in a standard cab, but bring a tape measurer to the store. Also, stay away from a geforce card since you don't know the TV-out chip since every manufacturer sells different versions. Some a great, some suck donkey d@!#. ATI is GREAT for tvout (real ATI not the licensed from ATI onces you can find on EBay). And after all this, you should be good to go.