In a similar situation I purchased my 3F speakers without hearing them first. Actually, I did not even hear any Paradigm speaker so I wasn't familiar with the "house sound" as you are.
You may be off to a good start if you already enjoy the Paradigm sound and have complementary equipment.
However, my setup wasn't ideal for the 3Fs initially. I experienced what many people say about them being bright. With the Persona line, you have one camp that saying they're bright and another camp saying they're smooth and great. It all comes down to setup!
Some things that helped a lot:
1) Careful positioning. Widening them apart, aiming a little more straight ahead changed the sound a lot.
2) Good speaker cables. I recently installed a pair of Audio Sensibility Testament Bi-Wire cables, which had a great impact on the overall tonal balance of the speakers. More lows-mids, smooth highs. This ended my use of DSP to "fix" the treble.
3) Use decent interconnects/power cables with shielding. interference can also introduce distortion that can make the top end seem harsh.
These speakers are sensitive, and work best when those bases are covered, IMO.