your best bet would be to post it for sale in the source component forums http://www.head-fi.org/f/6552/source-components-for-sale-trade
but before you sell your F807 you may want to wait until you receive your A17 and have a chance to compare the two players
i've read in the forums here and seen in other online reviews by people who own both the A17 and either an F800,F880 or ZX-1 series player that the latter android based players have clearer resolution,more authoritative bass and much better soundstage.
granted we all hear different and as with any audio equipment YMMV depending on everything from your age to what headphones or iem's you use along with your primary musical preferences and so forth, but .if you sell your 807 now you may end up regretting it,whereas if you hold on to it until you have had a chance to familiarize yourself with the A17 then still want to sell the F807 that option is still there. i plan on pulling the trigger on an a17 later this year though will be keeping my F807 as it has great synergy with my grado's (and all my headphones really) and ibasso d2+ boa amp/dac. either way I'm interested to know your thoughts on the A17 when you get it.