I have listened to PMC LB1 Signatures, PMC EB1i and IB1, Proac Tablette 50 Signature and D25 and Harbeth P3ESR, C7ES3, M30, SHL5 and M40.1. I think the speakers mentioned in your list are all good speakers as it boils down to personal preference in choosing the right one that fits your listening criteria.
PMC speakers are quite power-hungry, even the small little ones with 4 ohm impedance and need a bit of power to come alive. They are more neutral and accurate compared to the warm Harbeths and have better bass response due to the TL design. The Harbeths present music with more emotion, has more in the midrange and are a lot more easier to drive. The Harbeths are also less picky on amplifiers and will sound equally good on lesser amps. I have not listened to the Proac D1 and D2 but reckon they will sound closer to the PMCs with more extension in the highs. The Proacs are also easier to drive compared to the PMC. Have not listened to Spendor but read that they sounded quite similar to the Harbeths -warm with low listening fatigue.
If you want to get a different sound from your 8 years old Proac Tablette 2000 Signature, I reckon the PMC, Spendor and Harbeth will give you more of that than the newer Proacs although the D1 and D2 are excellent speakers. No experience with Devore. Personally I would not go with speakers that have drivers smaller than what you have right now in the 2000 Signature(the DB1i and P3ESR have a 5.5" and 5" woofer respectively).
There is often a misconception that all speakers with metal dome tweeters will sound bright with high listening fatigue. Actually it has got more to do with the tweeter's crossover frequency that the designer has set on the speakers rather than the type of tweeter.
PMC speakers are quite power-hungry, even the small little ones with 4 ohm impedance and need a bit of power to come alive. They are more neutral and accurate compared to the warm Harbeths and have better bass response due to the TL design. The Harbeths present music with more emotion, has more in the midrange and are a lot more easier to drive. The Harbeths are also less picky on amplifiers and will sound equally good on lesser amps. I have not listened to the Proac D1 and D2 but reckon they will sound closer to the PMCs with more extension in the highs. The Proacs are also easier to drive compared to the PMC. Have not listened to Spendor but read that they sounded quite similar to the Harbeths -warm with low listening fatigue.
If you want to get a different sound from your 8 years old Proac Tablette 2000 Signature, I reckon the PMC, Spendor and Harbeth will give you more of that than the newer Proacs although the D1 and D2 are excellent speakers. No experience with Devore. Personally I would not go with speakers that have drivers smaller than what you have right now in the 2000 Signature(the DB1i and P3ESR have a 5.5" and 5" woofer respectively).
There is often a misconception that all speakers with metal dome tweeters will sound bright with high listening fatigue. Actually it has got more to do with the tweeter's crossover frequency that the designer has set on the speakers rather than the type of tweeter.