Originally posted by dsp52 1) a zoom in the 70-200mm neighborhood (I'm drawn to this one as it is close the the old Vivitar Series 1, 70-210mm, that I used to use many years ago);
I'd steer you towards any of the Pentax 55-300 lenses (DA, DAL, or DA WR). As modestly priced telephoto zooms go, it's very hard to beat.
Quote: 2) a wide angle in the 10-20mm range;
Pentax DA 15mm limited. The older SMC version is the one that most people covet, so I'd look for a good second hand version of that if I were you
(or one of the HD versions if you find one at a good price). It's small, it's sexy, and it just delivers.
Quote: and a 50mm prime lens that is at least f1.8 or faster.
Depends if you mean standard prime (e.g. 50mm was a standard prime in the 35mm film era, but the equivalent for the k-3 would be a 35mm lens). I'd still push you towards the 35mm f2.8 DA macro limited though, whilst not an f1.8, it would cover the street/macro side of things, and with the high iso of the k-3, it'll do a reasonable job in low light. Failing that, the DA20-40 (which is weather sealed, but lacks the macro).
Having used virtually all of the current Pentax lenses, I'd say go for a used DA35 macro first (image quality is exceptional, and it's versatile enough to fulfill most roles). Add a used 55-300 DAL or DA next, followed by a DA15 last. None of those options are weather sealed (well ok, you can get the HD WR version of the 55-300), but if you watch the market place or eBay, there are likely to be a few of the DA limiteds turning up at a reasonable price (people selling their apsc kit to fund a k-1)