There are a couple of limits, yes.
There is the maximum number of connections your hardware can process. A usual Linux box should be fine with a couple of thousands of connections, but a cheap router (especially wireless) might be overstrained by as little as 300 concurrent connections. When you plan on sharing and downloading a lot of files, than you'll have plenty of connections, but any somewhat decent hardware shouldn't have a problem with it.
Linux has a soft limit of 1024 for open files per user as well, but this can be raised with ulimit.
aMule itself might struggle with a very high upload rate, too. Expect a higher CPU usage than usual and a sometimes sluggish upload behaviour (i.e. some slots upload with a very high speed while others will be near zero). Try to set your slot allocation as high as possible as well.