I just found an interesting board which is comparable to Oak:
http://www.silica.com/products/highlight/product/silica-xynergy-board-stm32-meets-spartan-6.html
I think it's not such a bad deal for 199Euros. I imagine they are also going to release an F4 version soon.
\Me thinks that such a board could be really useful to implement a Logic Analyzer *grin*