RRS (who are well out of your price range) advise against using a ballhead with a monopod, and if you think about it, it makes sense.
A mono allows you to swivel freely in a horizontal plane, so you only need to adjust up/down. A ball head moves freely in all directions which is unnecessary on a mono.
So the Manfrotto 234 is ideal for relatively light setups. There is really no solution 
AFAIK other than RRS's for heavy duty applications, but the swivel on its own is USD150
I use the Manfrotto 234 on a Benro Monopod (MC-91n6). It works well for my uses, but then I don't have "field artillery" lenses
The link to RRS is 
http://reallyrightstuff.com/tripods/04.html for the heavy duty version and 
http://reallyrightstuff.com/tripods/03.html shows the Manfrotto, with their gear of course.
If you do decide to go the RRS route, I would recommend their lever clamps over their screw clamps. I have one of each (screw on mono, lever on tripod) and much prefer the ease of use of the lever clamp.