I was planning to mine on GPU's, 3 maybe  4 5970 or 6990.
FPGA's are to expensive because I get my electricity pretty cheap. And is there a secondhand market for FPGA's? Because if I spend 2000 on FPGA's and Bitcoin fails I'm stuck with very expensive hardware that nobody wants. Graphiccards I sell for a nice price but FPGA's???

Costs will be (EURO)
100 for a PCIe board with at least 4 x16 slots.
250 for 1200 corsair PSU
100 for decent CPU
50 for Mem
250/300 for4 secondhand 5970's
400 for 3 secondhand 6990's
7970 are to expensive.
Leaves approximately 500 for misc.

Looking in to P2Pool mining, looks good.
But is the reward as big as in centralised pool mining?