I think it depends on one's budget, room size and upgrade options. Assuming a budget of $500 to buy a new receiver and main speakers for a small to medium size room, I would get the Pioneer 516 or 816 and the Primus 250's. With a $700 budget for a slightly larger room I would get the Pioneer 816 or 1016 and the 360's. In either case I would upgrade to 360's as main and 250's as surround speakers as soon as possible (that's more or less what I ended up doing) !
My budget until now:
Primus 360's : $ 380
Primus 250's : $ 280
Sub (used) : $ 130
Pioneer 816 : $ 290
Cables : $ 60 (speaker cables and optical spdif cables)
Hi-Fi cabinet (used) : $ 100
Total : $ 1240. Approximately 2/3 of my budget spent on speakers. I wanted a 12" sub so I went with a used one, because a new one would have been too expensive. Imho a smaller sub is not worth adding to this system, since the 360's and even the 250's will go just as low in most cases, with reasonable efficiency.
The C25 will have to wait until 2007 I think...