Here's a post initially saying the Hsu STF-2 was a lot better than the Axiom EP175. However after they were both calibrated, he pronounced them equal (last post in thread):
http://www.axiomaudio.com/boards/showflat.php?Cat=&Board=HT&Number=34633&page=&view=&sb=&o=&vc=1
When comparing two subs, I'm not sure you should "feel" a lot more bass with one vs the other if both are properly calibrated. IOW if both subs are properly calibrated, when playing the same material at the same loudness, the bass response should be about the same.
If you want to feel more bass, that's perfectly OK; so do I. Just run whatever sub you have at +4db or so; that's what I do. I suppose at a certain point you'll reach the capability limit of the sub, and likely some have more than others. But for something in the EP350/STF-2/STF-3 range, I'd guess this limit would be pretty high at normal or even high normal volume levels.
