Originally Posted by Yooper
Well, that is a low ABV kit to begin with. A nice "session" beer!
I'd suggest that getting a different kit, that better suits your needs. The reason is that bumping up the ABV really isn't as simple as just adding more fermentables. You'd also need to add more hops, to keep the balance the same, so you'd be reworking the recipe. It's not uncommon for extract batches to finish on the high end of the anticipated FG. If you want more attenuation, you could try a different yeast strain but that might only give you a couple more points of FG anyway.
In other words, ditch the Brewer's Best kits (which are OK but not great) and get a nice kit from Austinhomebrew.com or northernbrewer.com. They have hundreds of great kits that will be much better than the Brewer's Best kits that come with canned LME.
See, I'm not talking about just this particular batch. I did a Holiday Ale from Brewer's best that was supposed to be 7-8%, and I think mine ended up to be something like 6.3%. It was a fine beer, but if I'm given a range for alcohol content, I want to be sure my processes are hitting that range, and I definitely don't want to have to modify the recipe to do that.
I think you're onto something with changing to a different kit. My homebrew shop does their own kits, so I'll give one of those a try for the next batch.