Definitely think that room placement is number 1. As for number two, it's sort of a toss up for me for room EQ vs. stereo subs. it depends a lot upon room setup.
Proper subwoofer placement gets you in the ballpark for flat frequency response. (OTHER) Parametric eq allows you to take multiple readings from different seating positions and apply a "best" frequency response (not necessarilyy flat) for those positions. I beleive an auto eq allows for only one spot to be effectively eq'd flat.
placement and eq. moving it around the room until you find the place that sounds best, because different rooms will affect the sound in different ways. Then, EQ to smooth out any peaks.
From most of my reading and personal experience I believe usign proper placement (trial and error) while using a tuning program or disc with an SPL meter. Next step would be to fine tunit it with a paremetric EQ.
With the "Other" being doing a manual set-up as many reviews (most) actually show that a receivers "Auto" set-up is still not as good as a good old manual set-up with a good SPL meter.
Subwoofer placement is very important since the low frequencies do bounce off everything. I like to play around with placement until I find the optimal position.
For a two years I put the sub under the components, between the main speakers, thinking it was the best position. I was wrong. Eventually, putting it in the corner was the right thing to do. Proper placement, while I can't explain how, did the job for me. I also think that having full-range speakers will provide good low-frequency sound without using a sub, at least for music listening.
Placement is key. You can't change the dimensions of the room, so the location of the sub is something that can be changed and has a great effect on freq response.
There is only so much you can do with placement at some point, and then you'll have to turn to another method. Using EQ is the most popular method, and its rather effective at that. You aren't really altering physics or solving the freq problem, but rather covering up the audible effect by increasing/decresing the intensity of certain frequencies. Your ears won't know the difference, though.
Choosing proper placement was a no brain er for me. It's clearly number one in the poll IMO. Time and again experience has taught me that. The second is EQ and I don't really know if auto EQ for subs is ready for prime time. At least for Audessey is not ready as it's implemented in my Denon 3806. It set all my my speakers to large, set the sub 5db hot with crossovers of 40Hz for the mains and 60Hz for the surround. Pretty bogus. So number two for me is EQ, not autoEQ, but manual EQ.
1st off may I say this has got to be the best contest I've ever witnessed on this site. Unbelievable! After getting my 25-31 a couple of months back I quickly realized that placement of the sub was the most vitally important task that any new sub owner should undertake. After placement I'd go with a dual setup just to ensure that you maximize your potential response, of course if the room and wife allowed I'd go with a quad setup .
I voted for proper placement and using more than one sub.
"Proper placement" because I believe it's the primary factor in achieving smooth results, but "More subs" because sometimes you simply can't get smooth response from a single location in a difficult room!
Proper placement is vital to getting the best performance out of a sub. I notice different subs require different placement, this can be very time comsuming but very much worth while.