You don't have to get an agnos head of course. If, as it appears from your choices, you are aiming for a budget setup then there are budget options. Mainly the nodal ninja, kinpano and the panosaurus.
Thinking sideways if you were patient you could get one of the panosaurous's the maker sells cheaper on ebay for about $80 delivered to argentina (240 pessos?). (Buying from the official site would cost about $95). It has a friction based rotator so you could just tighten the screw that adjusts the tightness and it would lock solid. Then stick it on top of your manfrotto rotator and hey presto a fairly precisise click stop rotating pano bracket!
Of course I don't know quite how you 300n rotator works so I don't know if you need to see the top or something. If you were not using the panosaurus rotator you could even trim off a fair amount of the plastic dial (its only plastic block) and reduce the footprint if its bigger than your roatator.
Of course the manfrotto probably comes with a profesional 3/8" screw and the panosaurus has a normal 1/4" socket so you would need something like this
in order to connect them. But they must be fairly common.
Anyway it would be a cheap option that let you use your smart rotator which is rated as one of the better ones, and often marginally better than the included agnos ones. The dissadvantage of the panosaurus is using more plastic it is more liable to shake and such than the agnos and not as sturdy. But the end effect would be much the same.
Obviously do your own research and assure yourself it is a practical idea before jumping in. But an idea.
panosaurus ebay site