I'm 5'11 and quite slender also. In my recent quest for a new suit I tried on suits from boss, ferre, gucci, armani and versace. Of these, the best off-the-rack fits were armani and versace suits. I can't remember whether the versace i tried on was black or a dark navy, but it was a really nice 3-button pinstripe suit and was only $1400can. The suit i ended up getting was a made-to-measure armani collezioni. Since you wanted specifics, the two cuts i liked most were New Comfort and Soft. The first two places you should start are Holt Renfrew and Harry Rosen, there are a couple stores in toronto so figure out where their main locations are. They both carry Boss, Armani, Zegna and Canali. Holt Renfrew carries an impressive list of brands but in my experience Harry Rosen has better selection and service. I've been to the Ottawa and Montreal locations of each store and in both cases I found better stuff at harry rosen. If both of your other suits are black i think you're best off getting a navy pinstriped suit as you need an interview/business suit. As for whether or not armani is worht the money, i think it is. Don't listen to the cheap suit advocates who tell you you're JUST paying for the name, they don't know what they're talking about. At your age though, it might be better to make sure the rest of your wardrobe is up to par before spending 2k on a suit. I say spend the most on what you wear every day.