B&W 803D - Best amplifiers to drive them


I actually have a few questions and I would really appreciate your wisdom on them:
1) 803D versus 802D - other than prize and size, is there is significant SQ difference, or if under budget constraints one settle for the 803D as they are 'almost' there?
2) Used 803D, how does one test a 2nd hand used speaker? Is there any way one can tell other than listening (auditioning) and visual inspection? Are there any key look outs?
3) The main question - which amplifiers drive the 803D the best? the rating says 50-500 watts, but that is a huge range at 8 ohms!!!!

Please do let me know
Thank you.
The nautilus top gives a superior touchable image of instruments and voices. Also the sound is more natural sounding. They only weak point of the B&W are there crossovers. They are poor in depth. I owned the 802N and the 800S for over 8 years of time. I listend to the 800D, but I did not go for it. I wanted to go to a higher level for the absolute sound. Then depth and a wide stage is a pre. B&W misses this important part, so I stopped with B&W. Musical Fidelity is a good option for your speakers. Wenn you have more money Pass Labs is a great match.
A substantial difference from 803d to 802d. If you can afford it buy the 802. I've owned and enjoyed the 803d for many years. I used a mcintosh 252 amp and c45 preamplifier. When I got the upgrade itch, went to the 802 diamond, and a 402 amp (same pre). I couldn't be happier. The sound and soundstage was a huge improvement. I use the 4 ohm tap on the amp bi wired with great results. I wish you luck on your search!
Thank you all. And Mark thanks for the specific responses to all questions. Appreciate all your help and advice.