Here was my Miata experience...
In 1989 when the '90 Miata launched I was 23 years old. OMG, I wanted one from the day I saw them. All Miatas had huge mark ups making $13.5k entry MSRP selling for $15k, maybe more. I watched the used market.
In my personal life, at the age of 26, I'd been dating the same girl for about 3 years. Done with college for both of us. Still living like college since I had a good deal with room mates and she had similar with her younger sister and friend as room mates. Starting to make real money. Watching friends getting married, etc. She wants a vacation and was her idea, we go to Vegas. I had one goal for this winter trip to Vegas for myself...I could rent a Miata, manual trans, from those places on the strip that rent Ferraris, etc. I paid about 4 times what a rental car would cost for one day with a Miata. I had one goal and that was I wanted to know if I could "live with" a Miata. We drove it north to some ski resort. Literally drove from dessert to snow.
In retrospect, she saw this trip as a "test honey moon" and I saw this trip as a "test honey moon" with a Miata. Less than a year later, in the spring of '93 I bought a '90 Miata base w/ 38k miles for $10k. Just months after that, we split. She knew I had some money saved and was hoping for a ring. I spent it on a Miata.
I still have that Miata today. When I bought the Miata I was lucky to have a company car with my job. I had not even owned a car for the 2 years previous (just using company car.) Being that I am in Ohio (salt), I put the Miata away every winter and just went back to the company car only. Free gas in that company car too so it really got used for anything that was not top-down driving.
I discovered/leaned to autox in that Miata. Discovered GRM too. In the following years, autox took a back seat to sailboat racing but I loved driving that Miata 1 hour to the lake to go race someone else's sailboat. Driving a Miata to get to a sailboat and back is just about my definition of a perfect day.
I autox'ed the Miata in stock class because I didn't want to get in too deep into the money race. I also didn't want to alter the car too much and make it less reliable or less enjoyable. A lot of my joy came from the fact that the car was so good in near stock form. Good being that I could just turn the key and it would perform. Sure, I could have made it faster like turbo but then it seems to require tuning and chasing down injector issues, etc. What I really wanted when I bought the Miata was a Triumph TR250 but even in 1993, all of these were 25 years+ old. I wanted a car I could drive, not a car I had to work on.
I think I had a 4 year loan on the Miata. Once it was paid off, I just kept it. When I left the job with the company car, I was driving my sisters cast off '90 Geo Prism that she had run into the ground. That got me over the hump and then I got into a '95 Civic Si and Miata. I got rid of that for a '97 Nissan 240sx. At one point, in my early 30's and single, no kids, I owned a 3 cars: '90 Miata, '88 MR2 SC and '97 Nissan 240sx. All rwd and all generally 2 seat. The 240sx was the "winter driver" and DD.
Yeah, I recommend getting the ND. I think you have your head on straight. I also agree with keeping it stock and keeping it reliable. You have the wild builds to scratch that itch of modification.
I also think the Miata ND is a good image (right image) car. You could buy a Boxter for less but I bet your employer or coworkers will see the Porsche as "eccentric". Your co-workers will think you are making too much. Even the more expensive Miata will be seen as more sensible and be percieved as costing less than it does. The newness of the Miata will make you seem "dependable." It's unfortunate if even the best maintained car makes you late due to a break down but the commoners will just say something stupid like, "what do you expect, your car's 20, (30), (40) years old. Miatas are cute and not threatening. A used Camaro SS could be bought for similar but that can have a douche-y image with it.