Amplifier for Monitor Audio RX 8 system

How do like the job your A21 is doing on your L/R mains now? If you're happy, you can expect the same level of performance from the A51 - a very fine 5 channel amp indeed.
I currently use a Pioneer Elite VSX 52, similar to your 53, as my pre/pro hooked up to a Parasound 5125 power amp and am extremely pleased with the results. The A51 with its increased wattage and Class A-A/B biasing would be a whole new level of performance. So I personally I would opt for the Parasound A51.

I would not be swayed by claims made by an audio salesman who frequents this forum that Parasound is a 2 Dimensional brand. I have had and heard many amps over 30 years and never seen a specification for dimensionality. Whether an amp produces 2 dimensions, 3 dimensions or even multi-dimensions is nothing more than the subjectivity of the audio salesman. His much coveted 3 dimensions also seems to exists with the brands he sells but not with brands he does not. He will also tell you he knows this from many years of listening which again amounts to nothing more than perception, because that is all it is. Without published specs, how does anyone know the dimensionality of an amp unless they take the word of someone is selling it? The last time I listened to someone who said "Bo Knows", I bought a pair of Nikes.

The A51 is a fine multi channel amp used by some very well known Home Theater Mag reviewers in the their personal systems who use it as a reference amp against other models. These same gentlemen also write for their sister publication, Stereophile.

Regarding using an AVR as a pre/pro, many of us do and I personally like Pioneer Elite products and their proprietary MCACC. It does a good job. So don't be swayed by slams against Pioneer either. To be frank, I don't know why they were even made as you indicated you will get dedicated pre/pro eventually. You initiated the conversation about amplifiers.

Good luck in your decision and happy listening.

"Without published specs, how does anyone know the dimensionality of an amp unless they take the word of someone is selling it?"

What specs do you look at to find the dimensionality of an amp?

It is very simple; you test and listen to the amps. I alwys use speakers which can bui;ld a big stage. So you know if they are 2 or 3-dimensional.I can sell what I want, because the company were I do business with has it all. But I do not sell amps which give a lower level in performance anymore. The same as for speakers. I want my clients to get the best results for the money. The thing I hate most in this business is the many average amps, speakers, cables etc. Many people spend a lot of money in audio. Wenn you listen to the end results it is often quite average or poor. We had a client with the Focal BE 1027. Also these speakers can give a deep and wide stage. He had a Pioneer surround amo of 2500 dollar. The stage was flat, so full 2-dimensional. Wenn we connected the Onkyo TX-NR5010 it went to a much higher level. Better dynamics, more resolutie and space. And also depth and a better sound. The class D sound of the Pioneer had not emotion. Like everything sounds the same. For me it is very simple how it will sound. And what are the limitations.

Per Bo...

"It is very simple; you test and listen to the amps."

What tests are you performing and what test equipment are you using? If you are just listening, then your assertion that some amps are dimensional and others are not is purely subjective.

Per Bo again...

"For me it is very simple how it will sound."

And in this statement, you actually admit that your opinions are purely subjective.

Bo, I don't mind you having a preference of one amp over another and then choosing to be a dealer for those brands. Its your prerogative. I don't mind you even recommending those brands. I do mind that you sell your preferences by slamming the competition and by using "made up" specs like dimensionality - something that there is no specification for and therefore cannot be measured. So in the end, all your claims about multi-dimensionality in an amp is nothing more than your subjective opinion.

You may be more successful by siting the factual information about why you "perceive" one amp to sound better than another. You know, things like build quality, amplification class, type and size of transformers and caps, watt output, current output, damping factor, s/n ratio, etc.

Good luck with your audio dealership.

Hi Zd542

"What specs do you look at to find the dimensionality of an amp?"

Not sure if your directing this question to me or Bo. If to me, I never worry about the dimensionality of an amp. I worry about whether it can adequately drive the speakers I will be using. So I look specs at wattage, peak current, damping factor, s/n ratio, etc. I also consider build quality, class type (I prefer A/B over D), reputation, etc.

Dimensionality is nothing more than the soundstage being constructed in your listening environment. The speakers and room itself are far more critical in constructing a deep soundstage than the amp. Processors and room correction is another matter entirely as these can affect the soundstage.