TL;DR: Buy the best one you can find in your local market. You have a lot of options given your budget.
Long version:
It boils down to "it depends." Do you wrench on your own cars? Do you prefer taking it to the dealer or an independent shop to take care of it for you? Or a combination of both?
I've owned two Porsches, previously a 996 C2, and now a 986.1 Boxster S. I can do basic maintenance and stuff and they are easy to work on, and lots of parts available, both factory, original parts, and aftermarket. Porsche is awesome for supporting their cars for a very long time. Both my cars have been trouble free. They will all have their weird quirks, but nothing that should leave you stranded, unlike an Alfa Romeo.
For $25k - $60K, you have some options, but ultimately, you need to ask yourself, what are you hoping to achieve out of the car? You can have a lot of fun in a base model Boxster, or a 987 Boxster like in your example. Buy the best model you can buy, but more importantly, when it comes to Porsches, buy the seller, and buy a car with a stack full of maintenance logs.
A lot of people give me a huge WTF look when I say this, but when I had my 996, it was hard to enjoy in the city. You're stopping every block in traffic and you're never really getting out of second or third gear.
Shop around and find a good example. If it's a short term commitment, find one that you can re-sell. $180K is a lot to throw towards a car, but if you have the means to do it, go for it. They are fun cars, and even more fun on the track. (Remember - only track a car you can afford to lose in a crash.)
I'm on the hunt for my third Porsche (not trying to flex or anything.) But I'm looking to get into a more competitive class with my local PCA club, and eventually get my race license to participate in club racing. My 986 Boxster is dual duty for track and street. I would like a 996 again, or a 997, but the prices are getting close to one another these days, but of course, there are a variety of factors that play into the prices. 997.2 prices are still demanding a pretty penny, and going back to my rule, it's a car I can't afford, or don't want to lose in a crash. Hard for me to boot around town in a 997 to get groceries and whatnot. It'd be a pretty boring drive and likely any wrong move will result in jail time or whatever.
Edit: IMS and Bore scoring - I'm not a big subscriber of these two items. My 996 was ok. And so was my 986. Bore scoring - most cars will have them, so it's a matter of when, like Traum said. I'd happily buy a 997.1 with bore scoring within limits, but that's just me, so buyer beware. Also, as Traum mentioned, newer cars will require that stupid PIWIS computer to work on. They are not cheap to come by, so you need to take it to a shop.
Edit 2: A lot of guys I go to the track with have over 180,000km on their 987 and 997 original engines, and all are original Canadian cars. Is there bore scoring? Yes, but these guys are wringing their engines to red line and over revving it like crazy. So far, so good. But take that with a grain of salt.
I was close to getting a Panamera as I had a really good experience with one a while back, and still really enjoy them, but insurance is a bitch, and they are total money pits. Porsches are the worst. Be prepared to be poor. Hope that helps.