You can search ebay for "iraud 1000W". Currently there are boards for 1000W at € 52 and for 2000W at about € 88,26. And you may need something like a SMPS800R (connexelectronic). Plus a speaker protection board.
Schematics of those amplifiers can be found in the web once you know what to look for. Iraud amplifiers are an old, yet good solution. The ready made boards may need some rework though, as they take the low voltage supplies from the high voltage rails, which isn't very nice.
Regards, Dieter