The 7250 will provide the rated amps (220wpc, I believe) into 2 channels @ 8 omhs; into 4, they'll go to 350, again, I believe. Offset this with the 89db, which is one or two below the 'norm'.
It works that you set the volume for clarity and articulation: fancy words for hearing all of the music. Also, it works that HT is less precise than music: we know the music: Beethoven's sixth or Brubeck's Take Five. As such we can tell when music is 'missing'. HT is not this way; other than voice, we would only miss the big stuff.
This becomes a financial question, although less so with the reasonably-priced B&K components. If you are serious about your music: sit quietly for hours listening to Miles and other wail, soulfully counterpointed by piano: then by all means go get some headroom and articulation.
One alternative is to get another 7250, then bi-amp the Contours (if you can) in a Passive, Horizontal manner: put a Y connector comming off your pre-amp for each channel, then run the 5 channel output from one amp to the LFs of the Contours, and run the other 5 channel output to the HF. This will improve imaging, as well as ensure that the LF & HF have enough juice (and the Contours have the necessary terminals). Again, it depends on your wallet.