So, time to talk about my direction for the NC. My overall vision for the car is subtlety - I want something that you wouldn't look too closely at to begin with, that doesn't stand out particularly on the street, but when you focus on it is a dark and beautiful car.
For now I am working on wheels, suspension, interior, stereo. I am not too focused an engine mods at the moment, although in the future I would like to redo the exhaust including headers, and change the intake. I may consider a turbo in a couple of years as well, depending on what's available at the time.
Firstly wheels - I spent quite a while agonising over wheel choices and colours, and in the end went with a set of gunmetal 17x8 +44 Rota Grids. In my opinion, grids are the best looking wheel you can put on an MX-5, they are just such a clean and subtle look. I do realise that wheels are an entirely subjective subject, and not many people will agree with me, but this is what I feel best fits the style of the car. Rotas are also a little maligned, but for me they are the perfect choice. They are very well made, despite what some say, and have the added bonus of being super easy and cheap to replace if I damage one. Most of all though, they look amazing. The first pic in this thread shows them on the car. I ended up keeping the same size tyre, which is the stock Michelins in 205/45/17 (I plan to get Michelin PS3's in the same size when it comes time to replace this set). This means I don't need to roll the guards, as the wheels are a bit over 20mm further out than stock, but the tyres come in off the rim far enough to never touch, even with lowered suspension.
As for suspension, I have recently fitted a set of Ohlins DFV's. They obviously come highly recommended on these forums, and I have to admit to absolutely loving them. They are so compliant in normal driving, every bit as comfortable as stock, but the grip and steadiness of the car when cornering is a significant improvement. I have lowered the car from the stock SUV height as well, it is currently sitting at 335 front, 338 rear from the centre of the wheels to the guard lips. I did the whole suspension change and setup myself, it probably took about five hours all up. Bear in mind I am an aircraft maintainer, so am pretty comfortable with spanner swinging (I also did the engine change, computer and turbo setup on my old car myself). The current ride height can be seen in the first pic of the thread as well, although bear in mind the car isn't sitting on perfectly level ground. Here's another pic of the wheels and how they sit under the guards post suspension fit;

Next I'll discuss the interior a bit. I find there is a bit of overuse of plastic in the NC cockpit, and I really think that needs to be toned down with a few leather touches. So far I've had new shift and handbrake boots made up and fitted, and I've replaced the awful stock gear knob with a polished ally Voodoo (my favourite shift knob). I've also replaced the little panels on the forward part of the door armrests with piano black pieces to match the dash trim. I found these subtle changes have really lifted the whole interior (haven't got a pic atm sorry), but I do have plans to get more trim made. I was looking at this site,
http://www.redlinegoods.com/MiataNCshiftboot.php, and really like some of the items they have. I intend to get door panels (diamond stitched), a gauge hood cover, padded armrest covers, door pull covers (a big improvement over the horrible plastic on the stock door pulls), and possibly roll hoop covers and yet another shift/handbrake boot combo. I'm thinking black leather with dark blue stitching, although I'll probably make the door pull covers dark blue leather. These leather touches will really bring the interior up a level in my opinion, but keep the subtle look I'm going for. I still haven't made a final decision on this as yet though.