I have practiced Aikido and can honestly say if what you are looking for is something that is "brutal" then Aikido wouldn't fit what you are looking for.
I am personally a believer in the Aikido Philosiphy. As my Sensei had told me "The only way one can truely win is by protecting both himself, and his opponent". What he was telling me that if you can get the person coming after you to stop, while still having them able to walk away, you have won. Brutality though can be easily applied within the art, my sensei tried to reinforce the concept that aggression is not the answer to success in battle.
An understanding of the purpose of kata may be in order. A lot of martial arts have dropped kata from their curricula, but really, kata is very effective in training muscle memory for proper technique and understanding how movements in a given art naturally flow from one to another. Students are not expected to acutally use a kata in an actual self-defense situation. In my Taekwondo classes, our poom-sae (the Korean equivalent of kata) are used to develop muscle memory, as I've noted earlier, and when faced with a dangerous situation where there is no time to think, we execute our techniques instantly. We also have one-step and three-step sparring sessions that serve as a bridge between poom-sae and freestyle sparring. We are also encouraged to practice shadow-boxing once we've come to understand the flow of techniques after working out our poom-sae.
As far as brutality, or physically effective techniques, keep in mind that every martial art has its strenghts and weaknesses. Because of this, there really is no such thing as a "best" martial art. My instructor incorporates self-defense techniques from other martial arts into the primary curriculum to give us a more well-rounded experience. Our brown belts can kick to the head AND throw the other guy to the ground.
Overall, is Taekwondo effective? I don't know...I haven't had to use it...yet. But I'm sure that in a self-defense situation, I can hold my own a few minutes longer than I would have if I hadn't studied any martial art.
Bukinkan? Are you a nindger? I'm going to break out my martial arts elitist position and tell you that the most important question you need to ask of any organization you go to is: "Do you spar?" If you aren't doing fully resistant, full contact sparring because what you're doing is "T3h D3adlY" then you're being sold garbage. I've done a couple months of Aikido. I don't recommend it, as it is based on a compliant Uke and sloppy, unrealistic attacks.
I know you don't want sport arts, but I'd bet on a boxer over a ninja any day. If you like Aikido, think you should do Judo or Brazilian Jiu Jitsu. Getting thrown on your head a few times might clean out some of that BS about combat sports being useless in "T3h D3adLy Str33tz!!!"
I know very little about Silat, so I'll repeat what I said about sparring. There is no substitute for having someone actually trying to hit you in the face. The same goes for JKD. Bruce Lee's philosophy behind it is great, but it depends heavily on how the school trains. My Muay Thai coach is also a certified JKD instructor, so I can find out more about it if you'd like.
To acknowledge the above post, Krav Maga is good if you can find good Krav Maga. There are a lot of shady KM dealers out there now that it has gotten so popular, so if you choose that route, ask for credentials.
I warned you that I was going to go elitist. I regard anything with a connection to ninjutsu with immediate suspicion. I do find it pleasantly surprising that your sensei is encouraging cross training, so there's a chance that you're not being sold complete bullshido.
I really do think that you should look into combat sports if you get the time, since you seem to be a bit of a martial arts enthusiast. Not immediately or anything, just put it on the To Do list. If anything, it's your best chance at actually getting to use what you've learned, because unless you've got a job that frequently puts you in dangerous situations, it's not likely you're going to see many street fights.
bullshido - brilliant.
I've been a student of Aikido for close to 20 years. Obviously i wouldn't have stuck with it for that long if I didn't have faith in it. I will say that it has a very steep learning curve and most people find they can't do much with it until 4 - 5 years in. If you don't want to make that investment search other arts.
Overall, finding a martial art is a lot like finding a pair of shoes. They either fit you or they don't and the only way to know is to try them on.
I agree with Josh about sparring and boxing. I have seen many martial artist humbled when they have stepped into a boxing ring mostly because they tend to be slower than boxers. They can't block or punch fast enough to even keep up with lower level boxers (6 months to a 1 year in the gym). I have been most surprised by MMA fighters who struggled to hold their own in a boxing ring.
There is a lot of debate about which is the most effective martial art on the street, but when your opponent hits you with a knock out punch before you can do a fancy move, the rest does not matter.