Welcome to the forums! The ZP3 is a great phono.
There are two modifications that you can have done at the factory. First, beeswax caps, this is higher quality capacitors. Second, the 25th anniversary mod is a maxed out power supply.
I have not heard the difference between modded and nonmodded. Everything I've read is the mods take a great amp to the next level. bottom line if you can, just get the mods and enjoy.
If it's a possibility now, get the mods. If not you will need to send the amp back to the mothership and get upgraded at a later date.
This is a very long tread about the development of the UFO25th, after Steve finished that work of art, transferred the knowledge to his other designs and named them the 25th Anniversary Mods.
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1510887200