More fodder: The continuous power for the bm6500 is 110w IEC 8oms which as i understand it is around 55 RMS. 

My reading indicates that when amplifying voice speech, the speaker and amp RMS should match, however for most music you want  2* speaker RMS to Amp RMS to avoid distortion and damage and for DJ applications you'll want to consider even higher ratios.  This would make the 6500 a good match for S120 or even MS150s.

The proof of the pudding will be in the eating!

However, the beolab 8000 system was a tour de force, never matched in power or refinement by anything B&O made before or a couple of years after. It was the Beolab 5, or beolab 90 if you will, of its time! BM6500's internal amplifier is a souped up version of the amplifier that was in the smaller music systems, e.g. BC7700, at the time BM8000 was made. This is a nice sounding amplifier, but was made for smaller loudspeakers. 

If you want to use the huge MS150's, they will sound nice with BM6500. But it will lack the power and control BM8000 will have over them.

I like comparing BM8000+MS150 to a rolls royce, BM8000 the engine and the loudspeakers the carriage. When properly restored they will give you a great looking system and extraordinarily comfortable, effortless music reproduction with lots of power in reserve for when the music demands it. A smaller amplifier will be like a smaller engine in the rolls royce: it will lack control and power reserve.

Be aware, any 8000 system component, also the speakers, will now need service to perform at its best and/or prevent catastrophic failure. These are complicated machines and should not be serviced by beginners or standard repair shops. Take a look at beolover.blogspot.com, and there are more experts like him around the forum.

-c wrote:

I know it's more powerful but is it really sonically superior to more modern systems?

Simple answer - yes, absolutely. I have a full Beolab 8000 system and will never part with it. I no longer have a 6500 or 5500 system - make of this what you will!

As to your comments on power outputs, it's more complicated than it may first seem, but it is better to have an amplifier that is more powerful than the speakers can handle, than one that only produces half the power. It is easier to damage a loudspeaker by turning an underpowered amplifier up too high so that it is driven into distortion, than it is by over-driving using a powerful one.

Great information, I've read through the beolover site and was very impressed with the attention to detail, going as far as 3D printing adapters for the new capacitors to compensate for the size difference.....well that's someone I would let touch my equipment...if you get my meaning..

As to your comments on power outputs, it's more complicated than it may first seem, but it is better to have an amplifier that is more powerful than the speakers can handle, than one that only produces half the power. 

The internet is somewhat dangerous for me as i tend to do enough research to confuse myself, I've read a few theories around amp to speaker ratios.. More powerful amps, less powerful amps etc,  what made the most sense to me was something i read about speaker sensitivity or watts to decimal ratio.  The MS150 states the sensitivity but not the decibal relationship.

Also, the bm8000 is 4ohm while the MS150 are 8 ohms so why wouldn't i have to wire them in parallel to avoid over heating the amplifier?  

I have the utmost respect for people who can decipher this stuff.  

What the specifications mean is that the BM8000 will drive speakers that measure down to 4 Ohms in impedance - some amplifiers won't.

It will therefore drive the 8 Ohm MS150s quite happily, but only deliver 100W into them, rather than 150W. But don't worry; your ears will have given up long before that...😕

I wanted to follow up on your comments and thanks again for the insight.  Well by happenstance I would up with 2 BM8000 (one isn't working), and 2 sets of MS150s.   I hooked them up to my BM6500 and it sounded very nice and warm, when I hooked it to my BM 8000 it sounded less warm but really hit hard, filling in the upper and lower registers nicely without having to try too hard.

I'm still missing the warmth of my 6500, so I'm assuming a recap is in order. I'm confident with a soldering iron and a multi-meter but reading some posts it seems the BM800 is not for the faint at heart.  As stated however I do have 2 of these, would you recommend this as a DIY project? 

I wanted to follow up on your comments and thanks again for the insight.  Well by happenstance I would up with 2 BM8000 (one isn't working), and 2 sets of MS150s.   I hooked them up to my BM6500 and it sounded very nice and warm, when I hooked it to my BM 8000 it sounded less warm but really hit hard, filling in the upper and lower registers nicely without having to try too hard.

I'm still missing the warmth of my 6500, so I'm assuming a recap is in order. I'm confident with a soldering iron and a multi-meter but reading some posts it seems the BM800 is not for the faint at heart.  As stated however I do have 2 of these, would you recommend this as a DIY project? 

I remember talking to Tim Jarman about the 8000 compared to the 4400. We agreed that the 8000 was a receiver built without compromise - the transformer is massive! However we both agreed that it didn't sound as nice to listen to as the 4400. I run both at present and like them both. The 8000 is on bedroom duty as my Beolab 5000 has developed a fault  - and the 4401 is on music room duty - scandalously underused at present. The 8000 is lovely but is outrageously huge - This is my third 8000 - I keep selling them and missing them!!