For what you're doing you want a "real" character generator (to heck trying to use a stnadard computer for CG stuff, it never works very well).
I have a stand-alone Videonics Titlemaker.
Its titles look very clean and the type/edge/shadow options are plentiful.
It inserts in the line after the "switcher" or "mixer".
It keys the titles over the output inside its own electronics.
It can be composite (RCA jacks) or S-Video.
I don't know if these are still being built, but there are plenty still available.
Here are a couple of links:
http://www.atbatt.com/product/817.asp
http://shopping.msn.com/specs/shp/?itemId=169651781
http://www.videomaker.com/scripts/article_print.cfm?id=2424#videonics
