I have been using a MacMini as a source for external DACs for years. It has limited processing power but, for your application, it should be more than adequate. It has, also, been rock-stable and reliable.

timm68000 wrote:

I'm new to the digital music world. I mean I only played CDs and iPod... I just wonder if using a Mac mini is equally good?

You can get way better SQ and more features from other machines/devices than you can from a mini. Would need to know more about your listening habits / use cases before making a recommendation.

Moreover, the mini hasn't been updated in four years - it's even listed as a "Don't Buy" in the MacRumors Buyer's Guide:
https://buyersguide.macrumors.com/#Mac_Mini

$500 - $1K sounds like a waste of money to me for an underpowered machine that's four years old in design.

The sound/performance of a stock Mac Mini is ok, but to get really good sound out of one, you should consider modding/upgrading the stock unit. Mojo Audio have been doing upgrades for ages, but there are probably other good companies doing upgrades.