I have DiMarzio Fast Track 2 in my Kotzen Strat (bridge). I am very satisfied with the sound. It was great upgrade from stock SC pickup. In my Kotzen Tele I have DiMarzio Chopper T. Also very nice sounding pickup. The worst thing about finding the right pickup is that you have to try many to find the one which satisfies your expectation. The best way is to buy used pickups (@ half price) which you can sell quickly in case you don't like it.
Boith PU I mentioned are humbuckers in single coil format. They are dual-rail = coils are wound side by side. In this case, you can expect sound more like full size humbucker.
The other group of humbucker pickups in single coil format are those with stacked coils. Coils are wound one on top of the other. These pickups are hum-canceling, but the sound is more like traditional single coil pickup. If you want fatter sounding pickup, go for the first type: dual-rail. During the upgrade from SC I went for Paul Gilbert's Injector, which was stacked humbucking PU and I was not satisfied with the sound. So I went for FT2 for more fatter sound.
My 2c.
Don't limit yourself only to FT2, try to find good videos on YT of different dual-rail PUs. Maybe that will help you more. As I said, it's not easy task to find the right pickups, because one can not have them all to try... 
I hope you will find it. Good luck!
PS. For a very good pickup I would also definitely look after Wilde L-45 http://wildepickups.com/Wilde_Bill_s_Twin_Blades.html
It's Bill Lawrence Pickup. It can not be bad. IIRC, they have only one dual-rail or twin-blade (as they call it) model, so there it is not difficult to choose one. 
I didn't try or hear one yet, but from what i have read I think Bill's pickups are gems.
PS2. Bare Knuckle pickups are also considered top-quality. I found they also have dual-rail PUs: https://bareknucklepickups.co.…contemporary&pickup=cobra
Try the Harmonic Design Super 90. It's like a P90 for the Strat bridge. I have had his pickups in several guitars for a long time, and they are awesome.
better take some time to search and find yourself great boutique ones. they aren't more expensive than dimarzios or seymours
I'm in the process of changing my LP burstbuckers and just by looking national boutique pickups makers, I've heard tone that do not compare with dimarzios or seymours
I bought a 1992 Tyler recently that came with a Seymour Duncan mini-JB in the bridge. The bridge/middle combination isn't that great if you want quack, but the bridge has grown on me. It's very hot and compressed sounding to me, but I like it as its own thing. I wouldn't go for it if it was my only strat though and you want the classic strat sound.
A common mod is to put a bottom plate on the bridge pickup (Bare Knuckle sells them, among others), to increase the magnetic flux through the coil. Else I agree you could contact a boutique winder who can recommend something specific for your needs.
A few suggestions from my own experience:
-Suhr V60LP bridge: definitely fatter bust still a single coil. Not bright but clear, with beefy mids and nice bass;
- Lollar Special: a P90 in a SC size. Beefier than V60LP and fatter;
- Zexcoils: they have several products. The buckers are real humbuckers extremely fat.
Thats great info !! I'm looking for a fatter sound, so look into the DiMarzio Fast Track 2..
Keep in mind that if you're going for a humbucker in a sc-format - you'll want to replace your electronics with 500k values - as otherwise, most of them will sound pretty lifeless and muffled.
From personal experience, I can recommend - depending on your taste - DiMarzio Super Distortion S, Tone Zone S, Chopper, Fast Track II, SD Hot Rails, SD little 59 - all good pickups, very different one over the other though.
You can check out the list of pickup makers I've been compiling over at TGP... maybe one of them will stand out.
Damn, I really should get down to posting some clips of my pickups on the Pickup shoot-out thread. If anyone else can contribute, that would be great as well.
