Krell KAV 250A Questions

I'm considering a Krell KAV 250A used but I have a few prepurchase questions.

1. I've read alot material that says you should at least have 2x the watt on the amp in relationship to the speakers long term power handling rating (i.e. 200W @ 8 ohms speakers powered by 400W @ 8 ohms amp). Is it true in practicality or just something that's theoretical. I have a 100W amp right now powering 200W speakers at 4 ohms would my sound improve from upgrading an amp?

2. Do amps actually sound different (i.e. Krell reputated as sounding bright and other amps that sound warm or otherwise)? I've read quite a few posts saying there is no difference between amp sound signatures short of a difference in power. Anyone have a real world experience with this?

3. Will the Krell KAV 250A be able to power B&W 802N? Anyone heard the combo can testify to this?