SET suggestions up to $3k (used)

I'd second the Coincident, my two pieces very nice. Whatever amp you purchase add boutique tubes to budget if not included in sale. You'll never hear full potential of 300B amp with second rate tubes.

Border patrol 300b. If your really patient you might find 1 in that ball park price.

Or a small power supply.👍

@dhcod 

If your speakers are legitimately 96 dB sensitivity or close that is a good start. Equally important (Arguably more so) how easily driven are they? I’m referring to load impedance characteristics/phase angles. This aspect has a significant bearing on the success of using SET amplifiers.

Another important consideration is the quality of the amplifier’s output transformer and power supply. Fundamentally key factors. This is the very last area for cutting corners. Take your time and do some reading and research. SET and efficient easy to drive speakers can be stunningly good if done correctly.

Charles 

I don't believe you would need necessarily need 8wpc for speakers with 96db sensitivity. You may want to keep your options open. I'm driving 99db speakers easily from a 45 tube amp - so around 1.6 wpc. 300B's are nice, but 45s and 2A3s aren't that far off and are still somewhat available as NOS without forgoing your child's education. My point being, when shopping tube amps, make certain to shop tubes as well.