If you like a sound that is more open and transparent with more air and high-frequency extension the SHL5 would be a massive improvement over the S8e. The SP series are more comparable to the Harbeth IMO.
If you peruse the archives you would notice some comments on the Harbeth being a more exciting speaker. The Spendors are more bland and laidback in comparison.
Spendor S8e review http://whathifi.com/Review/Spendor-S8e/
If considering the Harbeth, you probably already know the LFD is one of the most successful amp that matches Harbeth very well. If you like the way your Spendors are singing it would probably be wise to stick with them. If looking for more excitement then explore the SHL5.
If you peruse the archives you would notice some comments on the Harbeth being a more exciting speaker. The Spendors are more bland and laidback in comparison.
Spendor S8e review http://whathifi.com/Review/Spendor-S8e/
If considering the Harbeth, you probably already know the LFD is one of the most successful amp that matches Harbeth very well. If you like the way your Spendors are singing it would probably be wise to stick with them. If looking for more excitement then explore the SHL5.