Hehe, the party - yyyyyupp.
There are quite many Atari parties in PL, although mostly for 8bit machines, but usually with presence of 16/32.
There are more/less 50 people, not that bad for a classic computer(s), I'd say.
This particular party was actually the first edition but seems like there will be more, next years, so You have a chance.
This was the party's WWW page: http://derenegeracja.atari.pl/aktualnosci/en