You need a MegAChip to get more than 1MB chip mem in a rev. 6 board:
http://amiga.resource.cx/exp/megachip
8375 is not pin compatible with 8372A so do not try to swap those.
If you only have a few slaves crashing the machine, then perhaps those slaves simply do not support your specific setup? Most slaves were originally designed for 030+ machines since those with 68000 CPUs would normally use the normal floppy-version. Many slaves were later reworked to work better with 020 and 000 systems but there are surely still some incompatible ones out there.
There is also the option of finding a 2MB 8372B Agnus from a A2000:
http://members.iinet.net.au/~davem2/...-2MB-chip.html
Those chips are quite rare though so it is probably easier and cheaper to finding a MegAChip.