Xgrid and Logic Pro?

I don't know Xgrid, but Logic comes with the *Logic Node* application, making it possible to run plugins on a second ('slaved') Mac.
Also, those track counts really don't say much, the important thing is how many and which plugins you use on those tracks. 60 audio tracks without plugins should be no problem, even for an old G4 machine - but when you put a Space Designer or similar plugin on every track, your Mac might reach its limits soon.
and 'heard of many producers having prioblems" hardly sounds factual. The interweb is a very big and unreliable rumour and gossip creating entity. Provide a hard link to a well documented problem from a user who appears to know what he/she is doing, but do not come with this sort of 'hearsay'. It is almost always useless. Track counts are a bad way of benchmarking anyway, unless the conditions are very strictly lined out and followed.
If I try really hard, I could bog down a Mac Pro with just four tracks, by just choosing the 'right' plugins on each track....

Logic node is designed to do exactly what you are looking for, no need to attempt a roll-your-own solution for distributing processing across a grid because they built it in as a feature in Logic a few years ago. There are certain limitations to what kind of processes you can offload to a node computer, and you need to have a tight and snappy ethernet link up and running. But once you've set that up it works great. Any relatively recent Mac with gigabit ethernet makes for a good node processor. Not sure if Mac minis have gigabit ethernet, but if they do, then there's no reason why one or more of those little things wouldn't do the job nicely.