How Important is Dynamic Headroom?

I recently bought a B&K Reference 200.2. I liked how it sounded at the store, and, in regard to specs, I was impressed with its high damping factor (450). Also, it has 225 wpc into 8 ohms (375 wpc into 4 ohms). Hence, everything seemed fine.

I read the owner's manual, and it lists the unit's dynamic headroom as 1.2 db. I did a brief search of other similarly priced units, and 1.2 db would seem to be about average (or perhaps on the low side?). Anyway, how significant is this?

Very significant, think of it in this senario: you are entering a freeway where you need to get up to 70 miles an hour as quickly as possible so that you can merge into traffic without having someone ram you in the rear, or you have to accelerate and swerve to avoid an accident.

It's the same thing, the acceleration ramp and freeway speed is a swell in the music during a song. Can the amp handle it quickly and without straining or being driven into distortion?

Using that analogy: you are on the freeway ramp. you accelerate up to 95mph so you can 'pick your spot'.. as you enter you daub the brakes and join at 75mph ... so far so good... you are behind a truck and hate it... so you change lanes to pass.. you downshift and are passing but it takes time to just jump on it... lucky for you, as you and the trailer just passed a state cop who is gearing up to ticket the tractor trailer for going 80 in a 65 zone...
I would not worry about specs (which is all the query is about) If it plays well.. who cares? you are using maybe 3 watts most of the time anyway!!! (unless a heavy metal gearhead, or you like to impress your down the block neighbors with your loud stereo)
no worries.
Interesting...I have been an audiophile for a long time, and so I understand your analogies. The amp has four of the biggest capacitors I have ever seen ("beer can" types or perhaps a tad larger). Anyway, I cannot fathom this being the type of amp that would run out of steam during transients. We will soon see. I am waiting for my new preamp to arrive.

Your B&K 200.2 is a pretty potent(and musical)amp. While specs may be a deciding factor when all other things are equal, they don't tell you how musical an amp is. Only your ears can do that. Just sit back and enjoy that movie or music tonight.
One comparision may be the term "bloom" you read so much about in the press nowdays.
I think it is something to consider when shopping for amplifiers.
IMHO, headroom is very important in good sounding audio equipment.
Depends on your speakers.
True "Class A" amps like my Pass Aleph 2s have no headroom, by definition.
That is Class A.
These amps are 160 watts Class A, into 4 ohms, and I've never clipped any speaker I used them with.
See this thread. The bottom line: Dynamic headroom is a spec that is inconsistently defined and misleading. I would therefore suggest ignoring it.

Also, re your mention of damping factor, extremely high damping factors are meaningless, because the damping factor as seen from the woofer's perspective will be limited by the resistance of the speaker cables and the crossover inductor. And most or all speakers don't need extremely high damping factors anyway. See this thread.

Best regards,
-- Al
I thank all for the responses. My preamp is scheduled to arrive on Wednesday. I cannot listen to the big B&K until the preamp is delivered (I have no other preamp). I put quite a bit of thought into the changes I have made in my system, and I am thinking it should be my best yet...

Unison Research Unico CDP-->Canary Audio CA-200-->B&K Reference 200.2-->Ascend Acoustics Sierra-1

I also have a pair of Opera Mezza loudspeakers. Comparing them to the Sierra-1s should be interesting. I have two sets of interconnects: Enigma Audio Apex and the Anti-ICs (by Paul Speltz). My speaker cable is also by Enigma Audio.
I am also considering trying tubes in front of the B&K. The preamp I have picked out for this purpose is the Quicksilver Line Stage (non-remote version). My only concern is the issue of having too much gain. In fact, I will post another thread on this matter.