Your speakers are 4 ohm. Likely they drop below this at lower frequencies. Maybe that accounts for the comment you made regarding the bass being somewhat lacking. I would look for an amplifier that delivers 100wpc at 8ohms and close to 200 at 4ohms. I agree that the $500 budget increase will provide a greater return on your investment.
If interested in the Rouge Sphinx I would look into the V3. It sells for ~$1600-$1800 . Audio Advisor sometimes have an open box unit for sale just under $1500.
Buying use opens up possibilities, as per the several suggestions aforementioned.
Good luck in your quest and keep us posted.