Have you priced out what you could get for that hardware? On average?
Thats a good starting point, I'm debating the same thing myself.
Since my hardware, on average, is worth 5 times what I bought it for and with that; I could buy even more power!
ok well that's one of the problems we have
6 * Avalon Minis 60Ghz = 360Ghz = £3000 each = £18000
70 Blades 10Ghz each = 700Ghz = £350 each = £24500
1 BFL SC 60 = 60Ghz = £3600 each = £3600
2 Cubes 35Ghz = 70Ghz = £1000 each = £2000
all based on ebay prices
then we have the problem of turning the cash back into BTC
so we possible have a cash pool of £48000