Hello Mikey,
I can't recall what I said in the thread, but no matter--here's the lowdown (no pun intended!). There is no fundamental difference in the character of low bass sound because a sub fires downward or forward.
With subwoofers, the way the woofer pressurizes the air molecules doesn't really matter--except to the designer and the performance goals and costs he has set. It can fire downward, straight ahead, to the rear, or even inside the enclosure ( a bandpass design), venting the low frequencies through a port.
It's all a matter of trade-offs in design: the volume of the enclosure, the sensitivity you want to achieve, the degree of bass extension (is 20 Hz or below important, or will you trade off lower distortion, better sensitivity, and the ability to play cleanly at loud levels, for moderate extension to, say, 27 Hz?). For example, the Sunfire subwoofers really will produce 20 or 18 Hz from a tiny enclosure. But the trade-offs to do that are: a huge amp is necessary (1,000 watts or so) because the small box is very inefficient; an enormous and expensive magnet assembly; and the Sunfires won't fill a huge room at high levels with low frequencies. And the sub is very expensive. So you see? Trade-offs everywhere! Then again, it's so small, you can easily hide it out of sight. Big advantage, right? For some people, yes. For you, maybe not.
The SVS enclosures are round, fairly tall and fairly ugly (that's all a matter of degree; big black square boxes ain't so pretty either!). Everything I read about SVS says they do a lot of things well; so do Hsu subs. The Axiom EP175 supplies very tight musical bass--and it's clean, with no bloat or boom--to below 30 Hz, which is sufficient for all but one or two pipe-organ fundamentals and some very low-frequency effects. Then again, maybe you want those ultra-low frequency effects.
Never having heard SVS subs or compared them to the EP350 or EP175, I can't tell you how they differ. If you are getting two subs, I'd get two of the same brand and model. Using two subs, you can even out the effects of standing waves--areas within a room of selective cancellation and reinforcement of low bass frequencies--which occur in ALL rooms.
Regards,
