I like what Audyssey and similar products can do in a room, but it is a Band-Aid fix for real acoustical issues in your listening area.
Now, I voted for room treatments, but like so many others stated, it really depends on where you are at currently, or what you upgraded recently.
My first theater many, many years ago, had cheap KLH speakers that I had picked up, and a low end Pioneer receiver. At the time, going to just about any different speaker or higher level receiver was a great "bang for the buck" upgrade. I mean, I couldn't afford $40,000 in speakers, or $60,000 in amps and power conditioning, etc, so my "buck" needed some good "bang."
So I've got a 7.2 setup that costs about $4800 for the speakers and subs. Not "top of the line" like some people with a lot more bank roll, but definitely not crap either and from a couple of "great bang for your buck" companies. That vs. probably $300 in crappy KLH speakers that I upgraded from.
Upgrade cost for speakers about $4000 (treating the 2nd sub separately since it was a voting option). More than 13x what the KLH cost.
I went from that $200 receiver, to receivers in the $900 range, and I love the increased features and clarity. That is 4.5x the cost of the original receiver.
Single sub to dual sub upgrade has been pretty nice. Not "oh my gosh, that is awesome," but one of those things that helps to fix nulls and peaks in a room. Cost $800. That is 2x the price of the single sub.
Next up, room treatments. I have a partially treated room already with the front wall treated including bass traps. I still need to deal with some echo and reflections in the rest of the room. I am in the planning stages of that and just today figured out the number of panels, sizes, etc. I already had the placement figured out. Total cost for 8 side wall panels and 1 rear wall (thicker for some bass absorption) is $412 premade and shipped, or $235 if I make them and that even includes a custom printed image on the rear panel. Hmmm... They will be the cheapest upgrade of anything I've done. It will also tame the subwoofers a little more, make the speakers sound even better, and since the speakers are fed by the receiver, it will effectively be able to work better too since I can reduce or eliminate the need for Audyssey, and it will help make EVERY listening position (I have 8) sound better, instead of trying to make them all sound just "ok" with electronic room correction.
So where I am today, room treatments are by biggest bang FOR THE BUCK. Everything else was a much larger expense, and while important, I should get results that will equal the receiver/speaker upgrade improvements for a fraction of the cost.
For others that don't have a dedicated space, or a spouse that refuses to allow treatments, then it might not even be anywhere on their list of possibility, and thus already off of their list of coices to even consider voting for. That is their situation. Can't change that.
I haven't been so excited about the improvements I should be able to obtain with the acoustic treatments since I built the room and was blown away by my soundproofing results.
Oh, and cables? Bah... Again, those people with those $40,000 speaker setups can have their expensive cables. If there is any measurable positive effects of using expensive cables (despite any logic or slick marketing), the cost for the amount of *potential* improvement is ridiculously out of proportion.