Are there any speakers you have listened to or owned that you could compare them to? How did they sound vs the Polk and Klipsch speaker you listened to?
In the review, I spend quite a bit of space (relatively) comparing the SVS Ultras to my JBL Studio II. Briefly, my testing methodology was an ABAB and BABA setup for quick, comparative listening. Also, listening separately with and without Audyssey MultEQ engaged. Both were run full range and with an SVS PS12-NSD at 80hz. For critical listening, my material was a dozen or so tracks that I am very familiar with including Feist "Limit to your Love", Ani Difranco "Hypnotized", Soul Coughing "Misunderstood", Paul Simon "You can call me Al", Aphex Twin "Milk Man" and others.
I note that at lower volumes, I found I preferred the characteristic of the JBLs. They seemed to have a high-frequency edge that kept them lively and helped them sound more detailed.
Non-anechoic measurement showed a bit more energy at ~5-7k which might account for this. That said, at high volumes, this same characteristic became fatiguing and at very high volumes, the JBLs would audibly distort (most noticeable in the Feist vocals in the "waterfall in slow motion" passage).
The SVS, by contrast, had a more neutral, accurate response. They did not distort even at high volumes and were never fatiguing. As I made them my primary speakers for a few weeks, I grew more accostomed to the sound and did not miss the exaggerated detail of my JBLs as much. They had much better low frequency response, though that benefit was negated with the inclusion of a sub woofer. They looked great. Overall, I preferred them to my current speakers, and they've convinced me that my next upgrade, now that I've completed my projection system, will be new speakers capable of playing louder with a more natural response.
Specific to Polk and Klipsch: I have owned low end Polk bookshelves. I have heard Klipsch in the past at a friends house. In my Best Buy days, I spent much time listening to each as they were in the same room (but could not be moved to be co-located, see "complications below"). I have heard only low to mid-range varieties of each, costing less than half the SVS, but at a 4th of the value proposition relative to their performance, build quality, and appearance. That's not to say that each company doesn't make great speakers, just that I haven't had the chance to hear them.
If I were the generalize the Polk vs. Klipch sound I've heard, it would be that Polks had a greater sense of space with a warmer response (balanced mid/highs, strong mid-low) that it maintained off axis. The Klipsch had a more pronounced high-frequency response which gave a sense of more detail, but, likely do to the horn design, did not maintain that character off-axis. Both were good speakers though not in the same league as the SVS (obviously, given the price), though I would put the SVS more in line with the warmer (balanced mid/high, very strong low end), perhaps more accurate Polks rather than the Klipsch.
Now, the complications of comparisons in a nutshell: Acoustic memory is short. The Room/positioning can have a huge effect so the same set of speakers can sound very different when placed in different spaces; I was just in a space where moving a pair of speakers 12 inches yielded a much greater sense of immersion. Humidity, allergies, associated equipment...all can have a noticeable effect and when differences, even in direct comparison, can be slim to the point of going unnoticed, in-direct comparisons are very difficult.
Critical listeners can mitigate these differences by using familiar material: I always listen critically with material that I have heard in many rooms and on many systems. I listen for balance of elements, purity of tone, and a sense of spaciousness, among other things. I Listen to speakers from different positions and in different spaces if possible. Listen on different days. Essentially, this becomes a method of non-scientific summing, gathering as much experience as possible to attempt an overall impression. It is an imprecise science, and ultimately necessary for most buyers. In the end, we want a speaker that sounds great and is a great value, and we won't be doing side by sides. We'll just be sitting back enjoying ourselves and should notice the speakers unless something goes wrong. With the SVS, no matter what material I played or at what volumes, nothing ever went wrong.