Try a used Conrad Johnson MF2550 or MF2275/MF2275SE.
The MF2550SE will be a little over your budget; probably by $500 to $700 ($3,700 total), but the amp will keep up with some of the best tube monoblocks out there (upwards of $25,000). The MF2275 has less power and can be bought used for $1,200 to $1,999.
I had the MF2550SE and regret selling it to this day. While I prefer my tube mono-blocks, the solid state amp had its place in both my A system and B system at different times.
The MF2550SE will be a little over your budget; probably by $500 to $700 ($3,700 total), but the amp will keep up with some of the best tube monoblocks out there (upwards of $25,000). The MF2275 has less power and can be bought used for $1,200 to $1,999.
I had the MF2550SE and regret selling it to this day. While I prefer my tube mono-blocks, the solid state amp had its place in both my A system and B system at different times.