Bass response is better than expected, especially if you put these on a pair of 28" high Sound Anchor stands. Just had a listening party tonight with a tube integrated amp (Ming Da MC-88 in Triode mode) and the following speakers in a room 11' x 11' with 8 foot ceiling: Spendor SP1/5, Spendor 15-ohm LS3/5a, Spendor SP3/1p, and a pair of Green Moutain Europas. Previously I've had the Spendor S3/5s on those stands and they are stellar too. The LS3/5as had a surprising bass response in this size room, but the Sound Anchor stands were likely part of that.
As for your choice, I haven't heard the Harbeths, but the S3/5s are very nice. Not quite the same speaker as the old LS3/5a, or presumably the newer v2 Stirlings, but one reviewer nailed them with he called the S3/5 both transparent and sexy as all get out in their midrange. Listening to a sax solo on the S3/5s gets libidinous, but all these others offer much the same enjoyment with certain refinements for a bit more money.
As for your choice, I haven't heard the Harbeths, but the S3/5s are very nice. Not quite the same speaker as the old LS3/5a, or presumably the newer v2 Stirlings, but one reviewer nailed them with he called the S3/5 both transparent and sexy as all get out in their midrange. Listening to a sax solo on the S3/5s gets libidinous, but all these others offer much the same enjoyment with certain refinements for a bit more money.