You might want to play around with some basic brewing math. I kindof enjoy doing it by hand, but the beer recipator site (http://hbd.org/cgi-bin/recipator/recipator
) is very handy for calculating things. If you aren't ready to formulate your own recipes, you can just type in recipes from a book and get a feel for how it all adds up.
On the Beer recipator, you have to estimate your own final gravity--you can get an edicated guess at that number by multiplying the OG times the attenuation rate of your yeast strain.
1 lb LME in 1 gal water = 1.037
1 lb DME in 1 gal water = 1.044
So, if you used the 3.75 lb can and 2 lbs of DME in a 5 gallon batch, that'd be...
3.75/5 * 37 = 27.75 points for the LME
2/5 * 44 = 17.6 points for the DME
27.75 + 17.6 = 45.35; so that's an original gravity of 1.045.
As far as hoppiness, it's hard to guage except by experience with the pre-hopped kit, since you don't control the hops or how much of them there are.