@Zorba:
It wasn't the poor landless people who were the main reason of the collapse of the Republic, it was a few bickering Senators who were. Whenever a Senator wouldn't get what he wanted and he had some support of the broader public he always could return to the people and ask him for either a show down or just a confirmation (both nearly the same...) of their support for his case. The result would be that the Senate would find itself at stake, or so they saw it. The Marius Reforms only accelerated this, because of the fact that the Patronus Cliens system from then on extended to the military too.

A contemporary writer has critisised the practics of Roman politicians, he basically keeps going on and on about moral decline in the Roman Republic. But besides his constant nagging, there is something quite different, he gives examples of when the political system went wrong. His name is Sallustius.

Quote Originally Posted by Cheexsta
the borders of the republic were simply too far-flung for Roman citizens to really feel the need to join the army, since their main reason for doing so was to protect their own homes from invasion.
Well the Romans went to war mainly because of their plans to conquer foregn lands. With the exeception of the 2nd Punic war of course - but in that war age and property requirements were lowered so as to enable nearly all Romans to join the army.

Quote Originally Posted by Cheexsta
Without a professional force, I doubt the Romans would have been able to continue expanding beyond what they already had unless another faction directly threatened their homes.
True, exactly why Marius reformed the army: too enable more men to join it and thereby increase Rome's invasion powers.