Personnaly, I would go with the accord. It is larger, more
luxurious, and less of a "rice" look to it, if you are not in
this age group where you need to show  your virility via your
cars (if so, get a minivan.. ha-ha!).

I also suspect it handle / ride better than the SI on the
highway, and in general, and the insurance is less.

Also, it just looks sooo much nicer than the SI. And leather is
very very nice.

My 2 cents

I'm glad you chose a very good make to purchase your next vehicle.
Well, lets begin a breakdown of decision making shall we?

-Both vehicles weigh differently, the Accord w/ more HP/TQ probably
weighs more than the Civic but are their Power-to-Weight ratios the
same?
-The Accord also has a V6 compared to an inline 4 of the Civic, which
affects gas mileage (although Hondas have had a hot streak of
producing big HP cars with great mileage).
-Both vehicles have a 6 speed gearbox so there wouldn't be a
difference other than gear ratios and other racing associated
properties.
-They both have decent sound systems from the factory... although
given some time... someone will figure out how to put an aftermarket
system in the Accord.
-Sure, the Civic doesn't have leather for an option, but leather seats
are usually heavier than cloth equivalents in the same vehicle.

It really boils down to tastes. I have not had the pleasure of driving
the US 2006 Accord Coupe V6, as there were only Japanese versions of
the US Acura TSX to drive (badged as Honda Accord-Rs) while I was in
Japan. But I've "borrowed" a friend's Si and it has the feel of being
back in the 99-00 Civic Si. Very nostalgiac... oh... well I guess I'll
end it here as I can go on ranting about the greatness of the days of
yesteryear.

thanks for all the thoughts - I'm going with the Accord Coupe. I'm psyched -
I pick it up Saturday....

Actually at the dealer (at least in over the Houston) you can ask for
leather in the accessories. The Accord has got many luxuries over the
Civic Si, but they're both incredible cars