[Jeph]

You can get a 2000 (2.7) with 24k for around $24k. I did. Consumer reports seemed to dig 2000 best of the Boxsters (as of 2004).

Getting an S may be a bit of a stretch. I don't think the trade-off of performance vs. how many more miles will be on it (compared to a non-S) would be worth it. I say this because one of your objectives is to keep it for at least 5 years.

Be patient.
A hartop will most likely have to be purchased separately.
Though helpful, not even a PPI or detailed history will guarantee trouble free years of driving.

Good look, I look forward to your driving enjoyment.