For your body upgrade needs, I'd say go with K-7. The K-x is an awesome little camera which in my opinion, makes a superb 2nd/backup body although these days I shoot almost almost exclusively with K-x, thus rendering my K20D as a backup in a way
As for the flash recycling problems, I recently faced the same at a family event with K20D/AF540 but that was because of my poor choice of batteries and lack of preparedness. If you use a p-ttl compatible flash (Pentax AF360FGZ or AF540FGZ or others that I don't know about...) and use the right batteries such as Sanyo Eneloops, and crank up the ISO to about 400, you should be able to lessen the load on your flash and see recycling times of around a couple of seconds, as I have learned afterward.