I have just bought a set of GX100's and the GX150C Centre - I would say they are quite demanding speakers on your amp, so you need a good amp to drive them well after reading posts above - that is for music, not so much for tv
I have just biamped my LX83 and that has made all the difference in the world to a single run - and now I have heard them just start to sing as I expected and they give a very big sound. A pioneer amp is a good option with these speakers as the class D amps drives speakers cleanly, well they do in the 83. The level of control goes up a level when you biamp and that means much cleaner mids and top end
They are also very bassy so need a bit of space or use of the port bungs which is what I am doing - otherwise there is a lot of boom, the Rx6 will be same though, if your room placement/ room is too small for the speakers or generally boom - they are very efficient speakers and big is not always better - depends on your room and crossover point / setup / how you listen.
I demo'd them against the RX6 and to me the Rx6 sounded thin and lost by comparison which was weird as they are very highly regarded I was very dissapointed - however I realised after that was most likely due the speakers having that terrible metal link between the binding posts that they always come with and always makes the speakers sound terrible and untrue of the real world / their best why manufacturers why???
Where as the GX100 have proper links included which makes for a more honest demo. The PMC .22 I demod were the same the bit you wire into sounds good i.e treble, the other part that the metal link links to sounds thin and echo'y mid / bass driver in this case
Either way from that demo I walked away with the GX - however I spent more of my time demoing the GX50 but went for the 100 thinking the 50 might be lost in my room - boy was I wrong the bass from the 100 is like a floorstander which is not necessary in a 5.1 system crossed over at 80htz. The Gx50 will likely be much easier to drive given the smaller driver
Definately demo if you can - dont buy blind if you can demo as its a lot of money invested, the Gx50 sounds different to the 100 - more lively, slightly less refined lower cross over point and different again to the RX6. I think I went with the 100 as its most like the top of the range PL100 in spec - apparently the GX range is approx 80% of the PL range - I am not sure how true that is.
For a lot less money and if you just want TV / Films 5 Apex speakers would likey be more than good enough for you - they are great little speakers - really dynamic sounding - do not be fooled by their size.
With the GX you do need good gear to get the best from them, you can hear that as soon as you fire them up - the Apex are far more forgiving I think of source etc but dont be put off by that - they still sound Great!!!. The better the spaker the more the demands - sometimes less is more - you get better sound from lesser speakers thats driven with lesser gear etc but it sound better overall - what makes more sense