Well Geek I too think your best bet is to wait until the new speaker gets there, hook it up to your Denon, and throw everything you can at it and see if it meets and/or exceeds your expectations. If it does the job just fine, then save your money. If you feel it's clipping, or if it ends up shutting down on you (this happened to me once with my Denon 4802), then perhaps an external amp is just what the doctor ordered for you.
For me my Denon kept me happy 95% of the time. But I really like to crank my system up from time to time, and it left me wanting when I really pushed the volume up. So I went the Emotiva route (XPA-3) and it satisfied my cravings just fine. Like Dakkon said, an outboard amp isn't going to change the sound quality of your sound system until you're really pushing the volume level WAY up. Your Denon (and my Denon, and every other Denon) will be pushed into distortion when trying to extract it's peak power out of it. With the Emotiva running the show, if I'm pushing my system to the point that it's using say 150 watts of power (more than what the Denon is rated to produce), that's only half of the XPA-3's rated output (300 watts) at 4 ohms, so the distortion level will be much lower than if I were pushing the Denon to that level since amps begin to produce more distortion once it's being pushed to it's limits. Also, the Emotiva (or any other amp with as much or more power than the Emotiva) won't get pushed into clipping nearly as soon as the Denon will be.
But all of that depends on how high you turn that volume knob. That's why many here will tell you to see what your Denon does with your speakers at normal listening levels before you go out an purchase an amp. Because your Denon is pretty beefy, and will play louder than many here will EVER play it. So the question is, does it play loud/clean enough for your tastes? Or are you more like Dakkon, WID and myself and prefer something with a little more headroom so that you can really crank it from time to time without worrying about clipping and/or shutdowns.
Personally, I've been very happy with my Emotiva. However I don't recommend it for those people running Axiom's 4 ohm speakers since there have been so many mixed experiences with Emotiva amps and those Axiom products. I won't tell you not to try them out (they have a 30 day trial just like Axiom). But I won't tell you to try them out either. I would suggest you try Outlaw or Rotel for affordable amps.... Krell, McIntosh or the A1400-8 if you have the bucks for them.
But definately, just use the Denon for a few weeks or a month before you seriously consider any of those other amps.
