your thoughts about "hybrids" or larger than average bookshelves

Thank you for sharing your knowledge with me.  The Marantz PM 6005 puts out 45 wpc into 8 ohms and 60 wpc into 4 ohms, and has received very favorable reviews; Cambridge Audio CXA-80 puts out 80 wpc into 8 ohms and 120 into 4 ohms.  While neither of these are "double" their initial output, reviews have been very positive.  The speakers mentioned above are 88 db with the Wharfedales being 86 db sensitivity.  Potential problems?

I know of 50W amps that make others having double the wattage rating sound anemic when the kick drum starts chiming in. Wattage ratings can have little bearing on what an amplifier is truly capable of. Wattage ratings are often inflated to put gleam in the eye of the important guy, the consumer. You want (at least I do) an amplifier with a high current power supply, beefy transformers and out put caps that closer resemble soda cans. Or a much larger bank of smaller ones that wont let you down when you want to get down. As a rule of thumb look for amps that double down in output power ratings, or get close to that. When dropping from 8 ohm down to 4.

Sound waves behave more unfavorably in symmetrical rooms. Its a decent size space, it could be worse, a lot worse. You can improve upon room acoustics with upholstery, carpet, creative defusers and sound absorption panels that cancel waves disallowing them to reflect back into the bigger problem areas. Now while none of us, or perhaps just most wouldn’t have any problem slinging spongy room treatments up around the place. In a shared space life could get lonely doing that. This is when you have to start getting a little more creative. Type /acoustic treatments room acoustics diy/ into your browser. That should keep you busy for a little while.

The type of speakers you are referring to all benefit from high quality stands so don't forget to figure them into the formula.

My apologies; In listening it seems I prefer "large stand mounts"; the speakers above all have 6.5" or 7" woofers and are about 15" to 16" tall, > 8" wide and 11" to 15" deep, as opposed to 5.25" woofers that seem to be prevalent in standard size 12" high monitors; the manufacturer seems to have taken their $2500 floorstander and simply cut it in half, leaving off the final driver.  I am looking for a CD player ($500) and an integrated amp ($900-1000).  The room is not large so the speakers should be able to fill the room.  One shop recommended a Marantz PM 6005 (45 wpc) and a Marantz CD 6005.  Another shop ridiculed that suggestion and said 45 wpc is too low and would need a minimum of 80 wpc to drive a second pair of speakers.  They recommended a Rotel or Naim and an Oppo 103 CD player.  Why would a square room be problematic?  I listen to rock, classical, jazz, big band, a wide variety of genres.

"Large stand mount" seems more commonly used. You may or may not like Dynaudio BM15’s. You have yourself a nice square room. That may prove challenging to any speaker.

Just curious, what do you mean by "hybrid", are you referring to a speaker between a "bookshelf" and floorstander whatever that might be or are you referring to a specific speaker design that uses different drivers which doesn't seem to be related to your question?

By definition, a bookshelf speaker is one that requires something to sit on whether it be a shelf or a stand of some sort. I am not sure what a hybrid means in the context you're using it but maybe you might clarify that.

On a further note, your question is quite general without giving any information of what type of electronics you might prefer. You might want to provide more specific information otherwise you are going to get so many different opinions from so many directions that you might end up overwhelmed. Listening tastes and preferences in music would be helpful as well.