Check Last.fm. There are a lot of signed and unsigned bands in the groups with links to tracks/websites/myspace pages:
lastfm.pl/group/Polish+Metal+Bands/connections
Even with the signed bands, you can check out some of the shows and see the supporting bands to find new music.
Nothing will top Norwegian BM as I'm sure you know. Poland has Azarath, Furia, Behemoth and a host of other bands. However, I don't recommend 'screamo' bands. For me, I like a band that can break from the mould and carve out their own sound. The best instances are Windir and Kampfar from Norway.