Most improved last 10yrs: Speaker, amp, or pre?

Amps. Class D switching amps are a major innovation.

Sonicbeauty: Tough thread. I do not think that this question has a correct answer.

Mapman: Class D amps might be an innovation, but certainly not a sonic improvement.

Tube amplifiers with automatic tube biasing.

cartridges seem to have experienced the largest proportionate cost increases. I wouldn't say amps have improved much.

Not many categorical sonic improvements these days. The best sounded really good years ago as it does today. The categorical improvements are in areas of efficiency, cost, size, convenience, aesthetics, etc. but not sound quality.