Actually, even my hard of hearing Dad (has a hearing aid in one ear) could tell the difference between a high-end receiver and high(er) end separates. Granted, he didn't hear as much difference as I did, but he heard it nonetheless. With that said, he thought the compromise well worth the dollar savings. The separates in question would have run additional $3000. Pesonally, after hearing the difference, I couldn't have gone the receiver route.
It's all about your own experience and expectations. From my point of view, if you're going to spend a good chunk of money on speakers, why hamstring them will middle of the road electronics. I've rushed into purchases in the past to save a few dollars, short-changing one side of the home theater for the other, and have ended up disappointed.
While pre-amp outs on a receiver does provide an upgrade path, I'd still argue that the noise floor is going to be noticably higher with this than with a nice pre-pro and separate amplifiers. In addition to this, separates (and high end receivers) tend to have superior internals and greater flexibility (of particular note is speaker crossover settings... there is no comparison here between my existing Pioneer Elite receiver and an Anthem or even an Outlaw pre-pro). Internal components matter. D/A converters, in particular, make a difference.
I have no doubt that many people enjoy the Axioms using mid-line receivers. Many people also enjoy the Bose cube speaker surround system. It's all about individual taste and perception, and thus ultimately subjective. I also didn't mean to suggest that "it's not worth doing without separates", though I don't doubt I came across that way.
I thought it worth noting - particularly given the system mentioned - that noticably better performance can be had by spending a bit more, whether this be in the form of separates or a higher-end receiver. How many in here would try to talk someone out of the Bose setup and into a nice Axiom system, based on personal experience? This is exactly what I'm doing with the electronics side of things. Caveat emptor.
My slant on things is probably a bit different than most, but I can't imagine running a nice speaker system from a cheap receiver. If I can spend $3K for a HT speaker system (which is about what I'm planning), 50% of this amount isn't over-kill for the front end electronics (I'd argue differently if we were talking about a HT-in-a-box speaker system, in which case it's probably best matched to a cheap receiver). YMMV.
