hum..for filter just get the CIR-CPL filter...i think it is very usefull when u shooting lendscape.
if u dun mind getting another ND filter will come in handy too.....

i think the Olympus TCON 17 is 1.7x so 420mm x 1.7 = 714mm. i think it is very good for bird shot. too bad i had never try using 1 of it. but i say some bird shot using it with the FZ50 produce very great result.

for storage just get a databank (Hard disk) for ur unlimited storage...