I want value, not salesmanship Is the Olympus OM-D E-M5 possibly the best value for my dollar?

How much range do you want with your tele lens? more than your S5000? thats a 370mm equivilent at the long end so to match that on micro 4/3 you'd need roughly a 185mm lens, on an ASPC crop camera you'd need roughly a 250mm lens and of course a 370mm lens on full frame.

Also are you looking to take the pics in poor light? if you want more range AND to take early morning and evening shots then the cost of the lens may well far outstrip that of the camera so I'd judge alot of your purchase on that not the camera

Personally my feeling is that you'd be best off with a good crop sensor Canon(7D) or Nikon DSLR(D7000 or D5200), autofocus wise they still have an advanatge on mirrorless, the tele lens selection is better with alot more used stuff out there.

Another option could be to upgrade to a better fixed lens bridge camera, the Fuji X-s1 for example might not provide the same performance as those Canon and Nikon DSLRs but it would be a big upgrade to all areas(much better image quality, longer lens, more manual controls) from your current S5000 and would provide near 700mm range in a cheaper/smaller package than any interchangeble lens system.