McIntosh Announces Mc451 Dual Mono Power Amplifier

One nice thing about Mac is they don't drive their tubes hot like ARC does. The tubes in an ARC last about 2000 hours. I'm told (having not owned a Mac) that their tubes last much longer.  Also, Macs don't use a screen resister as a tube protector. When the resistor blows it flames up in a spectacular fashion. Sadly I do have personal experience with this event- twice as my bias was out of whack. 

Wow,,, looks so big and powerful. The "V8" engine of the audio world maybe?

As a factory-indoctrinated Mac sales guy, to those complaining about the appearance, I will guarantee they will not change it. It is a BIG part of their brand identity…you can buy a new Mac and integrate it with an older system, and it looks like it belongs. Huge brand loyalty builder. 
This new amp has an electronic xover built in, so to use it properly the bass speakers should be passive woofers without internal passive low pass filters. The upper speaker can be anything.  Who has passive subs, really?  Otherwise you’re messing up an engineered passive network if you “double cross”. In most systems you should not use the crossover. 

@crustycoot   Most of us understand the aesthetics are very important with brand recognition, just wish they could offer a toned down cosmetic version in some models. Almost purchased the C22 Mk. V preamp but the over the top cosmetics vs. the Mk. III version which had an appealing vintage look was the deal breaker. 

You can also use this like it’s two separate amplifiers. You can run to full input signals to two separate sets of speakers if you wanted to. Or you can do the Byam route. I did this with 2601 model blocks and a Mac 275. The sound was fabulous I’m sure that this is no less.