nah, then use some sugars with some good flavor in them
i'd rather use cane sugar or even brown sugar...i've read of other types of cane and beet sugars i'd like to use in my triples, too. my next dark strong ale will use the belgian candi syrup, which i believe is made with beets.
i despise the taste of corn sugar, and even though it ferments mostly out, i try to avoid using it in my beer. i hate it when you can still taste it a week after bottling when i'm seeing how my brew's coming.
Dextrose (corn sugar) is almost completely fermentable. That means corn sugar = alcohol and almost no flavor.
DME will provide fermentables and flavor. You will get less alcohol per volume from the dme, but you will also leave some malt character, which is pretty important for the beer.
Since you're using Coopers Hopped Canned LME (presumably), you may also want to add a little bit of hops too. It may help balance it. I'd recommend an ounce at 15 mins of boil left, which will add a little aroma, too. Ask your LHBS what kind of hops might complement the kit.
You could also just brew about 3 gallons with the hopped LME and get a real feel for the intended character w/out the "cidery" bite of the corn sugar mentioned above(it was noticeable to me and friends when I started).