Yeah, it'd only be pure speculation and a guess on my part. I'd venture that for just a quick burst (not a sustained note or passage), the A7-450 could probably deliver a higher momentary SPL than the PC13-Ultra DSP. If it can pump something close to its rated 1300 Watts into that 18" driver, it's just physics - that ought to move more air than the SVS Ultra!
But, like I said, I have rather serious doubts that it could do so with the same sort of low distortion, linearity, accuracy, transient response and certainly not in a sustained fashion.
As someone else pointed out, the A7-450 is somewhat similar in design to the old, discontinued Epik Conquest. Way back when, the Conquest was able to produce higher SPL than the old 750 Watt BASH amp'd SVS Ultra with the old 13" driver. Since then, the new Ultra has up'd its output by a good 3 dB across the board. And in that lower mid-bass region that you asked about, the new Ultra DSP models are hitting around 117 dB with around 6% distortion using a 2 meter ground plane measurement in a quasi-anechoic environment. That is crazy, crazy loud! Literally dangerously loud, as that sort of SPL could easily damage your hearing if it were sustained for 10 minutes or so.
In other words, if the A7-450 is roughly the same in terms of sheer SPL output as the old Conquest, the new SVS Ultra DSP is within about 1-3dB of it. That's still significant. 3dB more output means a doubling of power if we're just talking about Watts into a perfectly linear power response load. But I would venture that the 120dB or so output that the PC13-Ultra DSP could produce in your room is more than you could rightly stand for any length of time. It was more than I could tolerate in that dubbing stage!
So, like I said, if the A7-450 is around the same as the old Epik Conquest (which I don't know for sure that it is, but it's just a rough sort of estimate), then it might be able to hit something in the range of 123 dB at 50Hz in your room, while the SVS Ultra DSP will hit around 120 dB at 50Hz in your room (and that much is known for sure). Is that extra 3 dB in the lower mid-bass necessary (assuming that it's even possible, which I'm not certain that it is)? Is it worth giving up tight transient response, accuracy, linearity and 10-15% more distortion? Personally, I would say "no". 120 dB sustained output in room is literally painful and enough to damage your hearing within 5 minutes. It's also hitting that SPL with under around only 6% distortion, which means that you won't notice that it sounds "loud". We associate distortion with loudness subjectively. Something sounds "loud" when it is "noisy", which means full of distortion. With such low distortion, you'll literally be feeling the pressure waves from the SVS Ultra before your hearing warns you that it's too loud. Kinda scary, actually
So, once again, I'm making an educated guess about the A7-450 based on the old Epik Conquest. But with the same size driver and similar amplifier, I think it's a reasonable guess. The old Conquest was able to out SPL the old 750 Watt SVS Ultra by a little over 3 dB across the board. But the new Sledge amp'd SVS Ultra ups its output by about 3dB across the board. So it's pretty much in the same ballpark now. But the new Ultra is making that SPL with extremely low distortion and super tight, super accurate, linear response. That's something the smaller A7-350 certainly didn't match, and I've little reason to think the A7-450 would be significantly better in those areas.
120 dB in room at 50Hz. If that ain't enough for you, then I guess you just hate your eardrums
