No worries and thanks.
The two biggest upgrade was the AVR by adding HDMI capability and multipoint room correction and the Sony 4K player. I trust in Yamaha's build quality and none of these components, the 30 year old cassette deck which has not been serviced since I purchased it 3 years back sees daily use without a hitch.
Here's a report on the 400s;
http://www.hifi-classic.net/review/psb-400-119.html .They use the same woofer as the Alphas but they have a much larger cabinet, and produce noticeably deeper bass than the Alphas without distortion or sounding flabby, not that Alphas have flabby bass.
Here are the specs for the 400s
FREQUENCY RANGE
(Anechoic Chamber)
Response 38 - 21KHz
On Axes @0 deg +/-3db 55 - 21KHz
On Axes @0 deg +/-1.5db 60 - 21KHz
On Axes @30 deg +/-1.5db 60 - 21KHz
LF Cutoff -10db 38Hz
The Alphas
Response 50 - 21KHz
On Axes @0 deg +/-3db 68 - 21KHz
LF Cutoff -10db 50Hz
The Subsonic 6 frequency response is a follows.... 25-150Hz (+/-3db) LF Cutoff at -10db is 22Hz
The Subsonic 5 frequency response is a follows.... 30-150Hz (+/-3db) LF Cutoff at -10db is 25Hz
That might not seem like much on paper but I notice a big difference in those 5Hz. I was surprised how much difference there really was.