EAR, I have an RX-V1400 (almost identical to the RX-V2400), Axiom M60/VP150/QS8 and Hsu VTF-3R. I mainly like 70s and 80s popular music.
My summary of surround (paraphrased from the Longfellow poem): When it's good, it's very good indeed, but when it's bad it's horrid.
The few well-engineered, well-mixed multichannel DVD-A and SACD albums are very, very good. They open up an entirely new dimension of acoustic experience, yet aren't artificial or contrived. The problem is there aren't many of these, and I'd be concerned your favorite material wouldn't be available in multichannel surround for a long time, if ever.
That leaves Dolby PLII or HK Logic 7 to convert stereo to multichannel. My experience is with PLII; I've heard Logic 7 is somewhat better. PLII works well on some material, not so well on others. But it's rarely fake or artificial sounding like some DSP surround systems. Dolby was very conservative and it either works well or just doesn't work, rather than artificially forcing certain voices and instruments to the surrounds.
When playing surround from stereo material via PLII, many times I press the "direct stereo" to momentarily deactivate PLII and see which I prefer -- stereo or surround via PLII. Almost always (to my ear) I like the surround version.
Good stereo is better than mediocre surround, and there's lots of good stereo material. OTOH, if you go with a 5.1 config of M80/VP150/QS8, you'll have a good stereo config but also get surround as a bonus (for less than a semi-exotic stereo config).
There's a tendency to over-emphasize the delivery technology and under-emphasize room acoustics. I've reconfigured my system several times to different walls, positions, etc, and the difference is huge. That's with the same source material, amplifier, etc. I'd definitely recommend a professional acoustic analysis and room treatment. I'd submit a properly treated room with Axiom speakers will sound better than an untreated room with hypothetically perfect speakers.
YPAO is a nice feature, but the EQ part has significant limitations -- it's only 7 bands, and has often made mistakes on my room. E.g, selecting a 200Hz bass crossover, boosting one speaker by 6db and cutting it by 4db at the same frequency (??!). It's not a magic solution for poor room acoustics. The wiring, distance, and level checks are great.
In general my recommendation would be go with an Axiom M80/VP150/QS8 config and get a HK receiver with Logic 7 to maximize the stereo->surround experience. Combine this with a professional acoustic treatment of your listening room. Eventually when your favorite material is available in multichannel SACD or DVD-A, try that and see if you like it -- players are quite cheap in the context of your overall investment.
If you're uncertain about this, check the Axiom boards if there's a nearby Axiom owner offering auditions, who has a surround system with PLII or L7. Try out some of your stereo material and switch between stereo and surround modes on the amplifier. If none are nearby, you could still afford to travel a ways to hear it, considering the magnitude of investment you're considering.
