CDNN has P7's starting $599, but they're Euro-style heel-base magazine catches rather than American style trigger guard buttons. Presumably W-German police trade-ins. Finding an American button-style P7 in good shape, much less NIB, it'll be close to pushing four figures and blowing your budget. And I don't think they'll have the heat shield for the gas retarding/locking piston that the American market demanded for heavy range use to keep trigger fingers cool.
CDNN also has the Kel-Tec PF9 for $229. It's kind of a crap-shoot quality wise, and I'll second that it may not be a gun that will stand up to frequent range and competition use, but Kel-Tec with their legendary customer service will keep trying to make it right if you have problems. And it's the smallest locked-breech 9mm auto out there IIRC, save for the Rourbaugh, so for many the minor gamble is worth it. And it's not as if the Kahr hasn't had it's share of problems and QC issues too.
It's hard to say, and there's not enough time on the market to make a truly informed opinion, but of the three, my gut tells me that if its going to see significant range and competition use, the PPS is the one you'll be happiest with in the long run. The Kel-Tec and the Kahr, at least anecdotally, have that "I'm for carry, and a little range familiarization only" vibe about them to me. Frankly all the super compact 9mm's have some issues, IMO, you're just skirting the bleeding edge of the materials performance envelope for 9mm and locked-breech designs, especially with flexible polymer frames thrown into the mix. And the PPS is really not a super-compact, but just a compact with a super-compact width profile. They made the slide quite tall to get the extra mass and locking inertia that slightly larger compacts like the G26, Xd, and M&P Compact enjoy.
On that note, I don't want to expand the selection, and I like sticking within the poster's original question, but you may want to expand your search to the Glock 26, and the S&W M&P Compacts, they're not that much bigger or thicker, and may be shorter, or not as tall as the PPS anyway, and one of them might work better for you.
