You will be fine with those power ratings for the 803D's. One of the advantages of having bigger amps is that the dynamic range tends to be greater but that is applicable to all bigger amps and speaker combinations. You will be able to drive the B&W's with no problem. The question is if you will be happy with the combination at the volume levels you that sattisfy you. Most people have never heard a 10 watt driving a 90db speaker just to see if it can. I can assure you that I have experimented with many combinations and yes a 10 watt tube amp can drive a 87db speaker with a 3 ohm rating. Does it sound like crap, well sometimes, depends on how loud, at lower volume seems okay. The difference is in the dynamic range as I mentioned above with the bigger amps.
The story about power and speakers is the same to me as Muscle and Fitness magazines, every six months there is a new way to increase bench weight or bicep size, but after a years worth of the magazine, you realize that it is the same stuff, just presented in a different manner. You will too hear many opinions about what is the absolute best way in terms of power, only you can decide what will work for in regards to volume and musical satisfaction with those speakers. If you could do an inhouse or in store demo, ask to plug in the smallest flea watt amp available to satisfy your own curiosity. Trust me, you will be amazed.
Based on what you state about volume levels, you should be fine.
Rotel is good, but the "dual mono" Primare I30 is in another league, and will not have a problem driving the B&W 803D's in your apartment.. Low to mid level listening will be much better with the Primare I30. 400 watt mono blocks are not necessary for B&W 803D's in your apartment. In your apartment, my choice would be something solid state with very large power supply, and is class A with 100 watts per side... low to mid level listening does not get any better with this type of amp...IMO, anyway.
I would suggest addition of another amp for bass drivers, i.e. trying bi-amping. Natural choice in this context should be the Primare A33.2 (120Wpc).
Having pretty extensive experience with B&W (not exactly 803D, but smaller 803S - used to own them for 3 years), I have not impression that I30's current capability is sufficient for always power hungry B&W. My former pair of 803S sounded properly with Rotel RB-1090 or Parasound A-21, much bigger amps than I30.
Demianm: 20m2 is a rather smallish listening room. I hope your 303D aren't too big for it. Are you planning to accoustically treat the room? I suggest you look into that.
I'm not familiar with the I30, but owned Rotel RB1080 and B&W 804S, so similar but smaller and with the aluminum tweeter. I didn't like the trebble of that combo and replaced it for a 2 x 75 W tube amp (McIntosh MC275) and love the combo. Yet I'm experimenting with active biamping.
So will the I30 drive the 803D? Yes, no question. Will you be getting all the speakers can deliver? Likely not. Maybe you go step by step.
Thanks for all the replies. I kinda know what 100W RMS sounds like, but many people insist that 100w is too weak to drive these speakers. I know very well that 400w will give me lots of clarity at concert-levels when demoing the equipment to my friends with rock music, but the other 99% of the time I will be listening to jazz and other soft music at levels to maintain a good neighbour relationship. Right now I have a Rotel RB1062 at home and I am satisfied with the volume levels on my 90db speakers. It´s the harness and lack of soundstage that I cannot accept.
Space is also one issue for me, I would like to avoid separates for now so that my living room more or less stays looking like a living room.
Someone pointed out if I had any room treatment, well yes, there are panels at first reflections, and behind the speakers, and also 3 bass traps, helped a lot.
I am a bit hesitant to pull the trigger because I cannot try the Primare at home, and buying and selling it can be a bit costly, resale for the Primare is not so easy as another brands.
Got a Tact M2150 for my 802D's and it sounds wonderful!
Should do the same for your 803's.
Can be had in your price range used. (If you can find one)
Demianm: a Coda CSI integrated will do a real good job with your 803's, but you'll have to go over your budget just a little. There's one for sale here -check it out. I have nothing to do with the sale and I don't know the person selling it.
I used to own Primare A30.1 and have tried two Rotel amps and even though the Primare was better than the Rotels I dont think you will be getting the best from your speakers by using I30. It wasnt powerful (good) enough for my Dynaudio 1.3se, and your speakers are more demanding than mine.
In light of what is being said here, including your preference for integrateds, may I suggest you wait until you save more and get a large McIntosh or Classe integrated? these two brands are generally considered good matches with B&W (I own McIntosh with my 804). They will be WAY better than the RB1080 (which I used to own with the 804). You speakers deserve good amplification!
Hmmmm... Primare I30 will be very nice with the 803D at moderate to low listening levels for Jazz, chamber music and vocals, and will suffice for louder listening if not completely capable of convincing recreation of a full orchestra or the Who live.
For what it is worth, I think Dyn's are hungrier than B&W's. THat said, even though Classe electronics are distributed and often demo'd with B&W and the combination produces a very nice midrange, Classe's separates are really better suited for smaller scale music with the big B's, lacking some bass umph. I have not heard the 803D's with any Macintosh gear, but think that unless you want to go to some beastly integrateds like the Krell FBI, Plinius Hiato or a used Musical Fidelity KW, you are only going to get marginal improvements over the I30 with other 100 to 200 W Integratged solutions. The I30 is a really beefy little amp.
Yeah, the Primare I30 is truly an amazing amp. I have it side by side with a Krell 400Xi right now. They are both great.