I have Studio 80's and Studio 20's, have auditioned Studio 100v5's many times and have done almost all of my amplifier comparisons on Paradigm speakers. You do not need separates for those speakers in my opinion if you have a decent receiver - if you really want more power you should just buy a more powerful receiver and put the money for separates into something else that will make a bigger difference like calibration, room treatments, or better sub. Studio 100s' are very efficient too - the maximum power input that speaker can even take is only 230W and they will run very well on a lot less. Are you having to max out the volume on your receiver?
The 125wpc rating is almost certainly for 2ch, so it probably drops to somewhere around 90-100wpc with all channels driven. That particular receiver also is ~30lbs and has discrete amps, it has a pretty good amp section. Surrounds do almost nothing while watching a movie, I wouldn't worry too much about having enough power for them - again, your center and sub do the majority of the work in any movie.
When looking for HT upgrades (of any type), by far the most important thing is to make sure you can actually hear a difference in a properly set up, fair
blind test, repeatedly, over and over again otherwise you are wasting your money. The "blind" part is very important because once you have knowledge of which one costs more or is supposed to sound better, that can have a significant influence. This is best done in your own listening environment, but if that is not possible, any reputable stereo shop will set one up for you. The point of diminishing return in the HT world is extremely low, so if you are spending money on stuff like this make sure the difference is very noticeable
to you - not what the guy at the audio store claims they can hear or says you
should be hearing
That is the most important thing. Keep in mind that self proclaimed audiophiles and people who claim to have 'golden ears' have miserably failed pretty well every blind test I have ever read about with regards to both amplifier quality and speaker wire quality, provided it was set up in a fair manner (i.e. everything having adequate power).
At the very least, if you're for sure going to get the new speakers, get them first before buying a new receiver or separates and only upgrade if your current receiver doesn't have enough power, but I suspect it has more than enough.
Here's are the results of a well known amplifier test done by Bruce Coppola (the bookmark I had is broken but this is the jist):
Another article with an explanation of how amps can all sound the same, here is a Wikipedia entry on Bob Carver and his blind test amp challenges ($6000 vs $400 in 1985 dollars ($14,000 vs $900 2018 dollars). Spoiler alert, everyone failed:
https://en.wikipedia.org/wiki/Bob_Ca...ifier_modeling
Another blind test, $700 vs $12,000:
http://matrixhifi.com/ENG_contenedor_ppec.htm
The results were;
38 persons participated on this test
14 chose the "A" system as the best sounding one
10 chose the "B" system as the best sounding one
14 were not able to hear differences or didn't choose any as the best.
Once again, the same as random guessing.
And just for fun: Monster Cable vs Coat Hanger:
https://consumerist.com/2008/03/03/d...onster-cables/