Apart from size, all P3ESR, C7ES3 and SHL5 sound quite a bit different from each other. Hence I would suggest you pick one based on your listening preference apart from the size of cabinet to suit your room.
The P3ESR although a small speaker with limited bass response is very musical and engaging. It sounds more lively with a feeling of joie de vivre compared to both C7ES3 and SHL5. The C7ES3 is more dynamic and has quicker pace compared to the SHL5. The SHL5 throws a bigger sound than the rest but lacks a little PRAT compared to these two speakers. The SHL5 can sound little dull, smooth and flat with warm-sounding amps. With suitable amps like an LFD or Luxman(or the Naim) the SHL5 will sound more exciting, dynamic and upfront. Not too sure where your Linn amp sits but generally Harbeth speakers will sound good with most amps out there. They will shine with better amps although the designer doesn't advocate the use of exotic electronics to drive his speakers.
Best is to listen to the speakers yourself at the shows and dealers and judge for yourself. There is no substitute other than listening to the speakers to determine which sound suits you best.
The P3ESR although a small speaker with limited bass response is very musical and engaging. It sounds more lively with a feeling of joie de vivre compared to both C7ES3 and SHL5. The C7ES3 is more dynamic and has quicker pace compared to the SHL5. The SHL5 throws a bigger sound than the rest but lacks a little PRAT compared to these two speakers. The SHL5 can sound little dull, smooth and flat with warm-sounding amps. With suitable amps like an LFD or Luxman(or the Naim) the SHL5 will sound more exciting, dynamic and upfront. Not too sure where your Linn amp sits but generally Harbeth speakers will sound good with most amps out there. They will shine with better amps although the designer doesn't advocate the use of exotic electronics to drive his speakers.
Best is to listen to the speakers yourself at the shows and dealers and judge for yourself. There is no substitute other than listening to the speakers to determine which sound suits you best.