Since he is making the distinction between
want and
need, I suspect there is nothing wrong with the sound of his speakers - as then he would "need" an amp.
Want reasons I can think of for buying an external amp:
1) Assurance that you have more than enough power. I shuffle speakers around and like knowing that I have power to spare for any normal speakers.
2) Relieving the heat load from the AVR - All things considered, a $600 amp that can take some or all of the load off of your AVR's amp section is a worthwhile thing! In the case of Denon/Marantz, their ECO mode definitely cools the AVR down and if you have external amps, there is no concern of an audible effect from it.
And assuming a 7 - 10 year life for the pre-pro section, he should get this relief on two, maybe three AVRs.
3) if you have two units that can act as pre-pros, you can compare settings via a simple A/B input selector (choosing which pre-pro feeds the amp). For example, I plan to run some trials with and without Audyssey. I don't trust any comparisons that require a delay to switch wiring, and this affords level matched instantaneous switching between the two conditions.
I think it is great that we save people from wasting serious money on expensive amps that will do nothing for their sound, but just because we have a really great hammer doesn't make everything a nail!
The one you refer to is 5ch...is that what you require? Similar power/impedance capabilities?
I think the Outlaw 5000 is actually very competitive as a 2 channel amp!
Per the AH review, it produces 170WPC into 8 ohms and 230WPC into 4 ohms.
Aside from pro audio gear, at $600, not many amps can beat that.
Additionally, as Good4it mentioned, the 5000 also provides great flexibility, should needs change, with the honest 135WPC X 5 channels.