Congrats on your Apogees. Of course you happened to choose the toughest beast in their stable to drive...but... I agree with everything 'Ptmconsulting' says about Apogees. Everything; and yes, once you hear a well set-up pair there's a high likelihood you might also travel the perilous road to satisfied ownership.
As for the Scinnies,especially the 1 ohm (best sounding version, as compared to the 4 ohm) the good news is there are many more amps capable of driving them today than in their original heyday though most are solid state...these include the usual big hitters such as Pass, Classe, Krell,etc. as well as some of the newer Class D brands which are supposed to be pretty strong even into low impedances [but check with your specific models because even these guys aren't necessarily rating themselves as 'confidently stable' into 1 ohms these days].
On the other hand, seeking to enjoy Apogees with the beauty of tubes is, as we all know, a whole other can of worms. Simplest way, again as we are all well aware, is to simply put your favorite tube pre-amp in front of your SS amp and reap their beneficial influence slightly less directly...as many (thousands?) of Apogee owners have happily been living with for decades.
But tube amps? are few and far between for Ap's in general and especially for Scinnies.
A few approaches (none of which are necessarily cheap or easy):
One is to have your speakers completely rebuilt by either Rich Murry at True Sound Works or Bill Thalmann at Music Technologies where the actual process may make them somewhat easier to drive whether it's via slightly raising or at least marginally stabilizing their input impedance or actually increasing and/or somewhat stabilizing their efficiency. Hand in hand, both areas of improvement will make an originally almost insane amplifier task somewhat more possible.
I say this because when my [much easier to drive] Duetta Signatures were transformed into TSW's Duetta Ultimates both of these factors were improved as a result (Input impedance now stable between 3.8-4 ohms and efficiency now at a 'whopping' 87db)...
Another suggestion (also $$$$$ sensitive) would be bi-amping with 2 identical (powerhouse) tube amps so that the work load could be more evenly distributed. But they must be identical for this to NOT open up more trouble than it's worth. A pair of your VTL 450 Sigs would be a formidable scenario?!! yes?
Another choice, and perhaps either the hardest (if you can't find one,) or easiest (if you can) is to get a hold of one of the few truly capable big tube amps that could handle them. Only a few come to mind (though there are surely others I can't recall at the moment):
The Wolcott 220 monos (El 34 based) are supposed to handle low impedance loads very well and sound very good doing so.
The big CAT's have been mentioned...
The big VTL's : the 750's or Wotan as well as the big Manley 500's (maybe their 250's but I honestly don't think so unless you bi-amped as above, with 2 pairs...?).
Maybe those eccentric looking big V Shaped Wavestreams (really cool looking IF nothing else, and ultra rare).
And my favorites: The entire Tube Research Labs line of mono blocs (My guess is their stereo amp at 100WPC would probably be fine but moving up to their 200 Monos (my amps) and above (400's, and the king-of-tube-amp 800's) are certain to work magnificently)...
Big bucks for much of the above options but also big rewards if you invest that far...
This hobby is, after all, the poster child for "Law of diminishing returns".
Good luck and happy Lissn'n.
