The FT-03 Mini is a quality case and I'm happy with how my build (3770k on air, and GTX670) turned out, but there are lots of things to be aware of. Even though I've worked on a lot of small casess (mATX as well as proprietary Shuttle shoeboxes), mITX in general and the Mini Fortress in particular felt like starting a new puzzle, so plan ahead and don't take anything for granted. HardOCP and Overclock.net has good SFF forums. And definitely download the installation manual; it has a some best-practice tips worth considering. The case gives you a lot of options, but that doesn't mean all are possible at the same time.
The Fortress Mini's small footprint was the main appeal to me, even though it is larger in volume than most other mITX cases because of the vertical mobo orientation, and the top and bottom clearances to accomodate I/O, ventilation, and legs. Height matters because the cables sprouting out of the top I/O shield can come out of gaps located at the upper edge of the rear or sides, so the case will still be 'front-pretty' if you run them out of sight, but they will always be cascading down a good distance to the floor or desktop. The case's only USB ports are also at the top, so if you're using those or the audio ports, you'll have to deal with the same thing.
The clearance between the I/O shield and the plastic top grille is big enough to stash stuff like a wifi dongle on a USB cable, but maybe not a large thumbdrive plugged directly into a rear USB port. That also means little clearance for things like a DVI to VGA adapter. You can always leave the grille off for more room, if you don't mind the losing the clean look.
As for the insides, nearly all mITX mobos follow Intel's reference for cpu socket placement. Most aftermarket performance HSFs will obstruct the PCIe slot, and the vertical orientation may mean less leeway for rotating the HSF/waterblock. When I made my build months ago, only Asus had a board with a better socket location (eVGA announced one too, but wasn't out at the time). I had wanted to use a Noctua C-style heatsink from an old mATX machine, but I didn't fit on my ASRock mobo, so I was stuck with the stock HSF. Plan ahead.
The manual does mention H60 style water coolers being a good option, but I heard a lot of them had noisy pumps, so I stayed with air cooling. It also recommends using video cards with rear exhaust. Honestly, I think your GTX670 Windforce shouldn't be a big problem, because the 140mm bottom fan cycles air out the case pretty quickly since the interior volume is so small, but I don't know how adding a radiator for water cooling would affect that fan's performance. Plan ahead.
I also used the Silverstone 450 SFX modular PSU. I do not recommend it for several reasons. It had just come out at the time of my build, and like many other people, mine was noisy. Silverstone eventually admitted the fan profile was tuned that way because the 450W runs hotter and is denser internally than the quieter non-modular 400W model. Mine also has a bit of electrical whine, even when the system was powered down. Maybe the quality has improved since its introduction; I haven't followed up on it.
The modular PSU is actually a disadvantage for the Fortress Mini. I ended up using nearly all the cables anyway because the different connector types are on different cables. And these are short cables, since it's SFX, so even though the cables have multiple connectors, good luck reaching multiple places. Molex/SATA/PCIe power adapters may or may not help. The case really is that cramped inside. The modular connections add extra inflexible depth to the PSU, so it will be wedged super tight against the drive bracket. Sure, it's possible to eventually put it all together in the right order, but there's zero possibility of making any adjustment without dismantling it all again. Plan ahead.
I did not use any internal optical drive. I prefer using an external since I can move it around on to whichever machine happens to need it on the rare occasion. I feel the same about card readers. Even if I needed to use one often, I'd get an external reader and tuck it in the gap under the case. Leaving out the drive bracket opens up a good amount of space. I saw pics of people using full size ATX PSUs or push-pull fans for radiator sandwiches.
Hope I didn't sound too pessimistic. I actually quite like the case and it came out the way I wanted, other than my negligence on the HSF. Stock temps are fine, mild OC temps aren't bad with the Intel HSF; noise under load is fine, and the gentle woosh of the 140mm at idle makes the PSU tolerable, even at desktop ear level. Everybody that's seen it has had favorable comments. It's an easy recommend for casual users since that would be a simpler build, and a cautious recommend for power users.