With respect to power - the P3s are lower sensitivity but a pretty easy load for the amp. My room is about the same size as yours and I'm in an apartment where I have to consider my neighbors. 50 watts from the Naim 5i-2 and Simaudio i-1 were more than enough for me. Yes, more power will get you slightly better dynamics and a bit more volume, but the P3s aren't really made for extreme high volumes.
Here are my thoughts on the amps I've heard:
1. If you're looking for a tube-like character, then LFD is a great choice. It's more expensive than the others I mentioned, although I'm not sure about the pricing in Europe. I've heard the Mistral and the IV, and both were excellent. I actually preferred the Mistral with the P3s. Seemed like the IV was a bit bass light, but that could have just been system synergy.
2. Croft is great because it's got a tube pre and Mosfet power section. Rather than the Phono integrated, I'd recommend their Micro 25 preamp. It's got a fantastic build-in phono. It's not too expensive, so you could go with separates. And the Phono Integrates is a nice all-in-one solution. Downsides - no remote.
3. In the Rega range I briefly owned the Elicit (not -R), and it was nice but I found it a little forward and tonally lean compared to the other British brands. Reviews suggest the Elex-R and Elicit-R are similar sounding. The reviews also say the Brio-R has less of that leanness and had a decent phono amp. It also pairs well w/Harbeth. Used, the previous Brio-R model is very affordable.
4. Exposure: I've owned the 2010s2. It was a very nice, refined sounding amp. I don't know if I'd say it's tube-like, but it certainly didn't have the typical solid state sound, either. It's 75ish wpc, so you'd get slightly more power. The 3010 series is over 100 wpc, and the current 3010s2d is getting very good reviews.
5. Naim + Harbeth is a very traditional pairing. I have owned the 5i-2 and the XS, and I preferred the 5i-2 in my setup. Both have a very engaging presentation. The treble is a touch smoothed/rolled off, and I loved it. I tend to bristle at any added sibilance or brightness, and I could just relax into the music. I'd highly recommend their speaker cables NAC-A5 - cheap and a great match (obviously) with Naim. Some older models of Naim require these cables due to the electrical characteristics of the amps, but recent models don't have this restriction. And older models may only have DIN connectors. The Supernait 2 is apparently a fantastic integrated, but you pay for it.
Anyway, as you can see, although I'm from the US I'm big fan of the British sound. I think you're in for quite a treat when you find the right pairing.
Best, Scott
