Best Intergrated Amp for JMR Twin Sigs under $500?

Any suggestions for a used integrated amp that will match well with JM Reynaud Twin Signature speakers (91dB/1W1m,4 ohms)?

I feel like maybe my current setup is not realizing their full potential.

Ive tried (in order of preference):
1. Cyrus 2 integrated
2. ASL Wave 8s
3. B&K ST-140

Power amps were used with preamp section of Advent 300 or NAD 3020.

Budget is $500, room is small, listen at low to mid volume.

Thanks.