....I've spent some wheel time with an S2000, also.
I LOVE the S2000.
If it came down to Miata, turbo, SC, or otherwise, versus an S2000......Buy the S2000!
Those cars are awesome.
Now, having said ALL OF THAT in all of my above posts, my 2004 Boxster S is hands down THE best sports car I have ever owned.
These Boxsters are absolutely FANTASTIC vehicles. No other car drives like my Boxster, handles as sweetly, or has better harmony of controls.
The Miata is more FUN, but the Boxster is a better experience. I know that sounds at odds, but that's the only way I can describe it.
If you end up buying a Boxster, you will absolutely LOVE that car.
Just make sure you do your due diligence and buy one that has had all of the known failure points addressed, or you budget into your purchase price getting them attended to.
So, towards that end, budget for a new water pump, new Air/Oil Separator, new IMS if you don't want to risk a blown engine (only a 10% chance), new cam chain tensioners, and I'd replace the idler pulleys on the serpentine belt as I personally know of several that have seized and started engine fires.
Good Luck.
If you want a Boxster, buy a Boxster. I'm glad I did. Best damn car I've ever owned.