Yes that is a disappointing statistic but the team running that are concerned that it not be overloaded like the other one so they being prudent and making sure it stays up.
If you have the winmxgroup patch, it is pointing to all of the fully working caches so there should not be a problem.
As regards your question I can only speak in generalities here but cable /dsl lines are all winmx will allow you to connect primary with, as you then pass all the system/network traffic as well as your own.
I use 512 meg of ram and XP, although mx should run fine on 98/ME also.
I did have a few teething problems before I went XP with my modem flipping out but not had that problem for over a year now.
Our advice is that if your an unstable primary then by all means be a secondary, a weak network benefits no one.